Southern California 2011 edition Produced anddistributedby: in Putting downroots earthquake country Earthquake Safety! Seven Stepsto Includes the

Introduction Huynh, JohnMarquis,GlennSong,BrionVibber; Contributors: later editions)andJillAndrews,SCEC(firstedition) Producers: Writers: bers oftheEarthquakeCountryAlliance Earthquake Authority(CEA),withcontributionsfrommanymem- Emergency ManagementAgency(FEMA),andtheCalifornia Foundation (NSF),theDepartmentofHomelandSecurityFederal Survey (USGS),incooperationwiththeNationalScience and theDepartmentofInteriorUnitedStatesGeological Prepared bytheSouthernCaliforniaEarthquakeCenter(SCEC) property damage,orothereffectofanearthquake. of thishandbookdonotassumeliabilityforanyinjury,death, individual orastructure.Thewriters,contributors,andsponsors preparedness; however,theydonotguaranteethesafetyofan document areintendedtoimproveearthquakeawarenessand Disclaimer: headquartered attheUniversityofSouthernCalifornia. Science FoundationandtheUnitedStatesGeologicalSurvey, SCEC isaresearchconsortiumsupportedbytheNational by permissiononly. at theUniversityofSouthernCalifornia.Reproduction Copyright 2011,SouthernCaliforniaEarthquakeCenter Seismic SafetyCommission: Survey: James Goltz,KateLong,TerrieMonaghan; Emergency ManagementAgency: Dennis Sylvester,DougBausch,JeffreyLusk; Bob Simpson,DavidWald,LisaWald; Cox, KennethHudnut,SuePerry,KenRukstales,MichaelRymer, Larry Collins; Rocky Lopes; California: Authority: University: Vinci; (p. 14);andRobertZimmerman16,18,20,22). Punchstock (p.24);JereSmith(cover,p.2,3,32);Zeke Min JaeHong(p.30);StephanieLangley4,6,12,20,22,23,28); Ann ElliottCutting(p.13,19,21,22,24,25);DaleGlasgow26); Illustrators andPhotographers: Elizabeth Burrill Design: of theEarthquakeCountryAlliance Dean Reese,BrianLowe,JeffPrimes;andmanyother 2 Harvard: JerryTreiman,ChrisWills,CharlesReal; DentonDesignAssociates:MargiDenton, LucileM.Jones,USGSandMarkBenthien,SCEC NancyKinkaid; CandyMiller; LoriDengler; MarkBenthienandRobertdeGroot,SCEC(2004 Thesuggestionsandillustrationsincludedinthis Caltech:

County ofLosAngeles: SCEC (USC): Andreas Plesch,JohnShaw; Vikki Appel,EgillHauksson,Margaret KFWB: American RedCross: Insurance InformationNetworkof Ilene Cooper,ThomasHenyey,Tran FredTurner; JackPopejoy; Todd Connor(p.16,17,23); GregRenick,DeborahSteffen,

JoyceHarris,PhyllisTan, FEMA: California Earthquake California Geological HassaanSughayer, Humboldt State California PeggyBrutsche, Ready America: California USGS: members Dale

Why should I care? 12 10 8 6 4 Southern California SouthernCaliforniaearthquakesandfaults uueerhuks Recovering fromabigone One plausiblebigone Tsunami hazardsandother Future earthquakes is EarthquakeCountry safe andreducedamage,alsowhatweshould why weshould This handbookisaresourceforlivinginearthquakecountry.Itprovidesinformationabout more destructiveiftheyoccurdirectlybeneathdenselypopulatedareas. earthquakes. SomemayhappenbeforethenextSanAndreasearthquakeandcouldbeeven hundreds ofotherfaultsthroughoutSouthernCaliforniathatcouldalsocausedamaging While theSanAndreasismostlikelytobesourceofourlargestearthquakes,thereare catastrophe (seepages8-11). quake, andrecommendsmanywaysthatwecankeepthisnaturaldisasterfrombecominga describes ingreatdetailtheextensivedamageandcasualtiesthatresultfromsuchanearth- lifetime, andwillshakeallofSouthernCalifornia.AstudyledbytheU.S.GeologicalSurvey 1680). Anothermajorearthquakeislikelytohappenonthissectionofthefaultwithinour to theSaltonSea,morethan320yearshavepassedsincelastmajorearthquake(around Further southalongtheSanAndreasfault,fromBernardinothroughCoachellaValley area, sotherewasverylittledamage. (1857), rupturingthefaultfromCentralCaliforniatoSanBernardino.Fewpeoplelivedin California, thelastmajorearthquakeonSanAndreasfaultwasmorethan150yearsago in 1906.Over3,000peoplewerekilledand225,000lefthomeless.InSouthern Andreas earthquake.InNorthernCalifornia,thelastmajorearthquakewas100yearsago famous faults—theSanAndreas.However,fewCalifornianshaveexperiencedamajor Generations ofCalifornianshavebeen“puttingdownroots”alongonetheworld’smost What should I do? 24 23 drop,cover,andholdon. 22 20 19 18 begintofixthem. 16 14 to EarthquakeSafety The SevenSteps STEP#7:Whensafe,continuetofollowyour STEP#6:Aftertheearthquake,checkforinjuries STEP #5: Protectyourselfduringearthquakeshaking— STEP#4:Identifyyourbuilding’spotential STEP#3:Preparedisastersupplieskits. STEP#2:Createadisaster-preparednessplan. STEP#1:Identifypotentialhazardsinyourhomeand The sevenstepstoearthquakesafety disaster-preparedness plan. and damage.Evacuateifnecessary. weaknesses andbegintofixthem. care aboutearthquakesinSouthernCalifornia,whatweshould know aboutearthquakebasics. What should I know? Web Resources 31 30 28 26 Earthquake Basics atqae n als Information availableafterearthquakes Earthquake shaking Locating andmeasuringearthquakes Earthquakes andfaults do tobe

(back cover) 3 Introduction Southern California is SOUTHERN CALIFORNIA Earthquake Country EARTHQUAKES AND FAULTS The earthquakes of California are caused by We know that the San Andreas fault produces large the movement of huge blocks of the earth’s earthquakes and that many other faults are also crust – the Pacific and North American plates.

care? hazardous. However, it is often difficult to understand The Pacific plate is moving northwest, scrap- how to incorporate this information into our lives. ing horizontally past North America at a rate of about 50 millimeters (2 inches) per year. Should we care only if we live near the San Andreas About two-thirds of this movement occurs fault? Is every place just as dangerous? This section on the San Andreas fault and some paral- describes where earthquakes have occurred in the lel faults—the San Jacinto, Elsinore, and past and where they may likely occur in the future, Imperial faults (see map). Over time, these how the ground will shake when they do, and what faults produce about half of the significant may happen in a plausible “big one” on the San earthquakes of our region, as well as many minor earthquakes. Andreas. The last significant earthquake on the Why should I Southern California stretch of the San Andreas fault was in 1857, and there has not been a rupture of the fault along its southern end from San Bernardino to the Salton Sea since 1690. It is still storing energy for some future earthquake.

But we don’t need to wait for a “big one” to experience earthquakes. Southern California has thousands of smaller earthquakes every year. A few may cause damage, but most are not even felt. And most of these are not on “BIG EARTHQUAKES the major faults listed above. The earthquake

Don’t be fooled! ALWAYS HAPPEN IN THE EARLY MORNING’ map at top right shows that earthquakes can #1 occur almost everywhere in the region, on This myth may be so common more than 300 additional faults that can cause

MYTH because we want it to be What does it mean? damaging earthquakes, and countless other true. Several recent damag- small faults. ing earthquakes have been To become familiar in the early morning, so many with earthquake This is mostly due to the “big bend” of the people believe that all big vocabulary, you may San Andreas fault, from the southern end of earthquakes happen then. In want to read the the San Joaquin Valley to the eastern end of fact, earthquakes occur at all “What Should I Know” times of day. The 1933 Long section first. the San Bernardino mountains (see diagram Beach earthquake was at at right). Where the fault bends, the Pacific 5:54 pm and the 1940 Imperial and North American plates push into each Valley event was at 8:37 other, compressing the earth’s crust into the pm. More recently, the 1992 mountains of Southern California and creating Joshua Tree earthquake was hundreds of additional faults (many more than at 9:50 pm and the 2003 San shown in the fault map). These faults produce Simeon event was at 11:15 am. thousands of small earthquakes each year, and It is easy to notice the earth- quakes that fit the pattern and the other half of our significant earthquakes. forget the ones that don’t. Examples include the 1994 Northridge and 1987 Whittier Narrows earthquakes.

4 Why should I care?

Significant Southern California earthquakes since 1857 Date Time Location Magnitude 1. 01.09.1857 8:24 am Fort Tejon 7.9 2. 02.24.1892 11:20 pm Laguna Salada 7.3 3. 12.25.1899 4:25 am San Jacinto/Hemet 6.7 4. 04.21.1918 2:31 pm San Jacinto 6.8 5. 06.29.1925 7:42 am Santa Barbara 6.8 6. 11.04.1927 5:51 pm Offshore Lompoc 7.1 7. 03.10.1933 5:54 pm Long Beach 6.4 8. 05.18.1940 8:37 pm Imperial Valley 6.9 9. 04.10.1947 7:58 am Manix 6.5 10. 07.21.1952 3:52 am Kern County 7.5 11. 04.09.1968 6:29 pm Borrego Mountain 6.6 12. 02.09.1971 6:01 am San Fernando 6.6 13. 10.15.1979 4:16 pm Imperial Valley 6.4 14. 07.08.1986 2:21 am North Palm Springs 5.7 15. 10.01.1987 7:42 am Whittier Narrows 5.9 16. 11.24.1987 5:15 am Superstition Hills 6.6 17. 06.28.1991 7:43 am Sierra Madre 5.8 18. 04.22.1992 9:50 pm Joshua Tree 6.1 19. 06.28.1992 4:57 am Landers 7.3 20. 06.28.1992 8:05 am Big Bear 6.3 21. 01.17.1994 4:30 am Northridge 6.7 22. 10.16.1999 2:46 am Hector Mine 7.1 23. 12.22.2003 11:15 am San Simeon 6.5 24. 07.29.2008 11:42 am Chino Hills 5.4 25. 04.04.2010 3:40 pm Northern Baja 7.2 1 Earthquakes plotted on this map (at their epicenters) include: significant earthquakes since 1850 as red numbered circles corresponding to the table at left; earthquakes larger than magnitude 5.5 (1850-1932) and magnitude 4 (1932-2008) as orange and red small circles; and earthquakes smaller than magnitude 4 (1933-2008) as blue dots. While there are thousands of earthquakes shown, this is only a very small window Geologic rates on the earthquake history of Southern California! For maps of recent earthquake information see page 31. The rate of plate movement along the San Andreas fault, 33 millimeters (1.3 inches) PACIFIC NORTH PLATE AMERICAN each year, is about how fast your finger- PLATE nails grow. As a result, Los Angeles City Hall is now 2.7 meters (9 feet) closer to San 1 Francisco than when it was built in 1924. It would take a mere (geologically speaking) 2 million years for your nails to extend 100 kilometers (60 miles) from San Bernardino to Palmdale. It took many millions of years of movement on faults (earthquakes) to shape Southern California’s current landscape. 3 2 1 1 San Andreas fault

2 San Jacinto fault

3 Elsinore fault

4 Imperial fault 4

T

L

U A 1 F SCEC Community Fault Model This map shows the 3-dimensional

S SCIGN A DA E A GPS station R EV structure of major faults beneath Southern California. Vertical faults D N

N A

A RR

N IE such as the San Andreas (red band from top left to bottom right) are

A S S GA N Compression zone RLOCK FAULT shown as a thin strip. Faults that are at an angle to the surface are San Gabriel shown as wider ribbons as they lie beneath broad areas (the nearest Mountains SIERRA MADRE FAULT 0 60 MILES fault to you might be a few miles beneath your home). Areas that seem to have few faults can still experience strong shaking from earthquakes 0 60 KILOMETERS Los Angeles Basin on unmapped faults or from large earthquakes on distant faults. Pacific Ocean

SAN JACINTO FAULT

ELSINORE FAULT

1 A schematic block model of Southern California showing the motion of the Pacific and North American plates, and the big bend of the San Andreas fault where the plates squeeze together.

LEARN MORE: See the web resources listed on page 32. 5 FUTURE EARTHQUAKES more will occur in the next 30 years in Southern California. We know that Southern California is subject

care? to frequent—and sometimes very destruc- These results are incorporated into national tive—earthquakes. Forecasts of future quakes seismic hazard maps, used for implementing help us prepare for these inevitable events. building codes, setting earthquake insurance But scientists cannot yet make precise pre- rates, and prioritizing emergency preparedness dictions of their date, time, and place, so activities. These maps combine earthquake earthquake forecasts are in the form of prob- rupture forecasts with formulas for how Why should I abilities that quakes of certain sizes will occur shaking varies with distance and factors such over longer periods of time. as distance from the epicenter and local soil conditions (see page 30). The most comprehensive statewide analysis

Don’t be fooled! “AND THE EARTH OPENED…” of earthquake probabilities (see below), A seismic hazard map produced by the #2 determined that the chance of having one or California Geological Survey is shown at A popular literary device is more magnitude 6.7 or larger earthquakes in top right. Areas in red and pink are more MYTH a fault that opens during an California over the next 30 years is 99.7% likely to experience strong earthquake earthquake to swallow up (see map at lower right). The fault with the shaking. The map adds together shaking an annoying character. But unfortunately for principled highest probability of such earthquakes is the from all potential earthquakes. Smaller earth- writers, gaping faults exist southern San Andreas– 59% in the next 30 quakes will only cause shaking locally, while only in novels. The ground years. For powerful quakes of magnitude 7.5 larger earthquakes may cause strong shaking moves across a fault during or greater, there is a 37% chance that one or throughout Southern California. an earthquake, not away from it. If the fault could open, there would be no friction. Without 5 Seismology Monitoring instruments friction, there would be no provide a record of California earthquakes earthquake. during recent historical times—where and when they occur and how strong they are.

1 Geology Geologic field mapping and aerial photos trace out California’s many faults and document the accumulated slip in earthquakes over thousands of years. Color spectrum shows

1 Geodesy Global positioning system (GPS) rates of slip, from fast (purple and red) to very observations by satellite document how fast slow (dark blue). various points in California are moving (arrows) in response to the steady motion of the Pacific and North American tectonic plates.

6 Why should I care?

CALIFORNIA LOW > >HIGH Liklihood of Intense Shaking

3 Expected Shaking This map builds on the map of likely earthquakes below to show how those earthquakes will shake the region. Bands of highest shaking generally follow major faults, but shaking levels are also influenced by the type of materials underlying an area—soft soils tend to amplify and prolong shaking, even at great distances from a quake. In addition, deep soils in valleys shake more than bedrock in the hills. Unfortunately most urban development is in these valleys.

Earthquake Forecast

Multidisciplinary groups of scientists and engineers, each known as a “Working Group on California Earthquake Probabilities (WGCEP)” have developed earthquake forecasts since 1988. The 2007 WGCEP was commissioned to develop an updated, statewide forecast. The result is the Uniform California Earthquake Rupture Forecast, available for download at www.scec.org/ucerf. Organizations sponsoring WGCEP 2007 include the USGS, California Geological Survey, the Southern California Earthquake Center, and the California Earthquake Authority. The comprehensive new forecast builds on previous studies and also incorporates abundant new data and improved scientific understanding of earthquakes.

7 The Composite Forecast—UCERF The final forecast results from evaluating and integrating several types of scientific data. This map shows the likelihood of having a nearby earthquake rupture (within 3 or 4 miles) for all areas of California. Areas along major faults (numbered) stand out as having the highest probabilities for earthquake rupture.

7 care? TSUNAMI HAZARDS When should I evacuate? A tsunami is a series of waves or surges most commonly caused by an earthquake beneath Evacuation should not be automatic. Before the sea floor. Tsunamis can cause great loss evacuating you should determine if you are in of life and property damage in coastal areas. a hazard zone and consider possible hazards Very large tsunamis can cause damage to There are two ways to find out if a tsunami that may exist along your evacuation route. Visit Why should I coastal regions thousands of miles away from may be coming. These natural and official www.tsunami.ca.gov to find out if you live, work, the earthquake that caused them. warnings are equally important. Respond to or play in a tsunami hazard zone. whichever comes first. i Beaches, lagoons, bays, estuaries, tidal flats and COUNT how long the earthquake lasts. If you river mouths are the most dangerous places to feel more than 20 seconds of very strong ground Natural warning. Strong ground shak- be. It is rare for a tsunami to penetrate more than shaking and are in a tsunami hazard zone, evac- a mile inland. ing, a loud ocean roar, or the water receding uate as soon as it is safe to do so. If you are on unusually far exposing the sea floor are all the beach or in a harbor and feel an earthquake i Tsunami waves are unlike normal coastal waves. —no matter how small—immediately move nature’s warnings that a tsunami may be com- Tsunamis are more like a river in flood or a slop- inland or to high ground. ing mountain of water and filled with debris. ing. If you observe any of these warning signs, Tsunamis cannot be surfed. They have no face immediately go to higher ground or inland. A GO ON FOOT. Roads and bridges may be damaged. Avoid downed power lines. If evacua- for a surfboard to dig into and are usually filled tsunami may arrive within minutes and may with debris. tion is impossible, go to the third or higher floor last for eight hours or longer. Stay away from of a sturdy building or climb a tree. This should i Large tsunamis may reach heights of twenty to coastal areas until officials announce that it is only be used as a last resort. fifty feet along the coast and even higher in a few safe to return. locales. The first tsunami surge is not the highest If you hear that a tsunami warning has been and the largest surge may occur hours after the issued but did not feel an earthquake, get Off icial warning. You may hear that a first wave. It is not possible to predict how many more information. Listen to the radio, television surges or how much time will elapse between Tsunami Warning has been issued. Tsunami or other information sources and follow the waves be for a particular tsunami. Warnings might come via radio, television, instructions of emergency personnel. i The entire California Coast is vulnerable to tsuna- telephone, text message, door-to-door contact If you are outside of a tsunami hazard zone, take mis. The tsunami generated by the 2011 Tohoku by emergency responders, NOAA weather no action. You are safer staying where you are. earthquake off the coast of Japan caused dam- radios, or in some cases by outdoor sirens. age to harbors and ports all along California’s Move away from the beach and seek more in- coast. A dozen people were killed in California following the 1964 Alaska earthquake. Tsunamis formation on local radio or television stations. from local sources are also possible. Follow the directions of emergency personnel who may request you to evacuate beaches and low-lying coastal areas. Use your phone only for life-threatening emergencies.

4 The water bulge sends waves both east towards the coast and west 3 Eventually the stuck area breaks 3 How Tsunamis are Formed into the Pacific. The first waves along the boundary, causing a 2 Over time, the North reach nearby shores only minutes large earthquake. Like a spring, American plate is squeezed after the earthquake. The other 1 Gravity pulls the offshore Gorda the overriding North American and bulges up as the Gorda set of waves may damage distant and Juan de Fuca plates beneath Plate jumps upward and seaward, plate moves beneath it. coastal areas many hours later. the North American Plate. Most lifting the water above it. of the time the two plates are firmly stuck together along the boundary (red zone).

8 Why should I care?

1 mile

SANTA BARBARA SAN BERNARDINO VENTURA LOS ANGELES

Earthquake Fault Zone (EFZ):

RIVERSIDE see “sample area” SANTA ANA Area evaluated for Seismic Hazard Zones

SAMPLE AREA

SAN DIEGO

Seismic Hazard Zone (SHZ) 1 Faults, liquefaction, and landslides: Red zones are Earthquake Fault Zones with potential for see “sample area” surface faulting. Blue and green zones are Seismic Hazard Zones with a potential for landslides and liquefaction, respectively. Shaded areas indicate future Seismic Hazard evaluation and zoning.

OTHER HAZARDS Seismic Hazard Zones (SHZs) identify Earthquake Fault Zones (EFZs) recognize areas that may be prone to liquefaction or the hazard of surface rupture that might occur In addition to strong shaking during earth- landsliding triggered by earthquake shaking. during an earthquake where an active fault quakes and the potential for tsunamis along Liquefaction is a temporary loss of strength in meets the earth’s surface. Few structures can the coast, there are location-specific hazards the ground that can occur when certain water withstand fault rupture directly under their that can cause additional damage: surface saturated soils are shaken during a strong foundations. The law requires that within an rupture, liquefaction, and landslides. The earthquake. When this occurs buildings can EFZ most structures must be set back a safe California Geological Survey produces maps settle, tilt, or shift. Landsliding can occur distance from identified active faults. The that identify Earthquake Fault Zones and during an earthquake where shaking reduces necessary setback is established through geo- Seismic Hazard Zones where these hazards the strength of the slope. These hazards can logic studies of the building site. EFZs are may occur. State laws require that every usually be reduced or eliminated through narrow strips along the known active surface person starting to “put down roots” by buying established engineering methods. The law faults wherein these studies are required prior a home or real property in California be told requires that property being developed within to development. Being located in an EFZ does if the property is in one of these zones. You these zones be evaluated to determine if a not necessarily mean that a building is on a can also visit myhazards.calema.ca.gov which hazard exists at the site. If so, necessary de- fault. Most of the important known faults in has an interactive map for learning about the sign changes must be made before a permit is California have been evaluated and zoned, hazards where you live or work. granted for residential construction. Being in and modifications and additions to these zones an SHZ does not mean that all structures in the continue as we learn more. zone are in danger. The hazard may not exist on each property or may have been mitigated. Mapping new SHZs in urban and urbanizing areas is ongoing statewide. Current zones, as established by the California Geological Sur- vey, are indexed at www.consrv.ca.gov/cgs.

9 ONE PLAUSIBLE BIG ONE

As shown on the previous page, it is only a

care? matter of time before an earthquake strikes Southern California that is large enough to cause damage throughout the entire region. What will that earthquake be like, and what will its impacts be? Could this be Southern California’s version of Hurricane Katrina? Why should I What could be done now to reduce these 30 seconds 60 seconds impacts? These are the kinds of questions that motivated the development of the ShakeOut The “what if?” earthquake modeled in this Earthquake Scenario, a comprehensive study study ruptures the southern San Andreas Fault of a magnitude 7.8 earthquake, led by the for more than 200 miles (black line on map U.S. Geological Survey with the Southern below). The epicenter is on the northeast side California Earthquake Center, California of the Salton Sea in Imperial County, though Geological Survey, and hundreds of experts. strong shaking will be produced all along The study was the basis of The Great the fault as it ruptures through the Coachella Southern California ShakeOut, the largest Valley, into San Bernardino, across the Cajon earthquake readiness campaign in U.S. history. Pass and further to the northwest until ending near Lake Hughes west of Lancaster.

Lancaster

Santa Clarita

Oxnard

Los Angeles

1 Long Beach Shaking Intensities in the ShakeOut Scenario Earthquake An earthquake km has only one magnitude and epicenter but a pattern of shaking intensity that depends on several factors. The strongest shaking (red on map) occurs very 0 50 near the fault and dies off as seismic waves travel away. Away from the fault, in natural basins filled with sediments, some waves get trapped and reverberate, 1 Shaking Intensities in the Northridge Earthquake During the 1994 magnitude causing pockets of strong shaking (red and orange that in this earthquake persist 6.7 Northridge earthquake, intense shaking affected a much smaller area and mil- for as long as a minute. Ground shaking continues as the waves travel away, and lions fewer people. Northridge was not a major earthquake and very few people in this earthquake, total shaking lasts for more than 3 minutes. [Map credit: USGS] have experienced one. Even for Scenario experts it is hard to imagine what one would be like. Even for Scenario experts, it proved challenging to think outside the “Northridge box” while studying a much larger earthquake. [Map credit: USGS]

10 Why should I care?

90 seconds 120 seconds 150 seconds 180 seconds 210 seconds 240 seconds

As the rupture progresses it will offset the 1 Earthquake Shaking Animation These computer-generated snapshots ground along the fault by more than 20 show maximum velocity of ground motion as the earthquake waves move out feet in places, and bend or break any road, from the fault and travel through Southern California. Snapshots are taken at 30, 60, 90, 120, 150, 180, 210, and 240 seconds after the fault starts rupturing. railroad, pipeline, aqueduct, or other lifeline Yellow indicates the most damaging level, with orange and red also likely to that crosses the fault. Overall the rupture will cause damage. Note the persistent shaking in sedimentary basins where waves produce more than 100 seconds of shaking have gotten trapped and reverberate. To view the complete movie, visit throughout Southern California. As shown in urbanearth.usgs.gov/scenario08. [Images credit: Simulation by Rob Graves, URS Corporation, for the Southern California Earthquake Center on high-performance computers at the University of the large ShakeMap at left, shaking will be Southern California; images courtesy of Geoff Ely, University of California San Diego/San Diego strong along the fault but also further away Supercomputer Center] where soil type, thickness of sediments, and other factors amplify earthquake shaking. In some areas, the ground will shift violently back and forth, moving nearly 2 meters How to Use the ShakeOut Scenario (6 feet) in each second—shoving houses off The Scenario describes a what if earthquake, not a prediction. More than 300 experts foundations, sending unsecured furniture and from research, government, and private industry, led by the U.S. Geological Survey, objects flying. collaborated to identify the physical, social and economic consequences of one The overall shaking in this earthquake will be plausible earthquake on the San Andreas fault. The full report is available at more than 50 times the shaking produced by urbanearth.usgs.gov/scenario08. While this particular earthquake may never occur, the Northridge earthquake (see inset at left). that doesn’t limit the value of the study. In addition, large earthquakes create earth- quake waves that are never created by smaller Looking in detail at one major earth- When a major earthquake does occur, it earthquakes like Northridge. These long quake provides insight into how to pre- may be on a different fault, or create a period waves can cause damage very far from pare for the other earthquakes that may different pattern of ground shaking and the fault, and are especially damaging to tall occur instead. Thus, appropriate uses of damage. Thus, inappropriate uses of buildings or certain infrastructure. the ShakeOut Scenario include: the ShakeOut Scenario include: CUrban planning; CDeciding where to live or work; Finally, damage may also result when strong CEmergency response training; CConcluding you don’t have an earthquake shaking occurs in areas prone to landslides CSchool, business, and public earthquake problem; and in materials that are susceptible to drills; CChanging building codes; or C liquefaction whenever the groundwater is Prioritization of preparedness efforts; CEvaluating cost-effectiveness of mitigation. CUnderstanding potential impacts on financial close enough to the surface. Maps of areas and social systems; and where landslides and liquefaction are possible CIdentifying possible vulnerabilities of infra- in future earthquakes are available at structure, especially due to interactions www.consrv.ca.gov/cgs. among systems that are usually considered separately.

11 RECOVERING FROM A BIG ONE Thousands of older buildings will collapse in the ShakeOut earthquake, and another 45,000 The Shakeout Scenario evaluated all aspects will be complete economic losses. care? of the major earthquake described on the previous page to estimate damages to Earthquakes start fires in numerous ways, and buildings and infrastructure. From these earthquake damages to phones, roads, and estimates all other aspects of the study buildings enable fires to spread before help emerged, including emergency response in can arrive. In areas where there is strong the critical first week after the earthquake, shaking to start fires, and tightly spaced wood Why should I casualties, mental health and sheltering needs, buildings that allow fire to spread, the fires and the impacts on different sectors of the will grow into conflagrations, burning tens to region’s diverse economy. hundreds of blocks. Fires account for half of the ShakeOut Scenario casualty and loss The study estimates that should it occur, this estimates. earthquake will cause some 1,800 deaths and 53,000 injuries. Yet this terrible tragedy could This earthquake’s economic losses total $213 be considerably worse. By comparison, the billion, due to shaking damage and several similarly sized, 2008 Sichuan, China earth- other factors. Because fire damage is so com- quake may have caused 100,000 fatalities plete, the fires have the worst impact on the costs of replacing buildings and contents. The ShakeOut Scenario’s casualty numbers However, disruption of utilities is the main are a testament to decades of life safety reason that it will take a long time for busi- improvements in California’s building codes, ness to get back to normal. which have evolved as understanding has

Don’t be fooled! grown regarding building performance in One important result of the ShakeOut “BEACHFRONT PROPERTY IN ARIZONA” earthquakes. The intent of the building codes Scenario study is that the key to recovery lies #3 is to protect people during an earthquake, not with infrastructure: the essential facilities like The idea of California falling to keep buildings functional after the quake.

MYTH roads, hospitals and dams; and the lifelines into the ocean has had an Nor do the building codes fix existing build- that supply water, power, gas, and communi- enduring appeal to those ings that are now recognized to do poorly in cation. The more damage there is to infra- envious of life in the Golden earthquakes—it takes retrofitting to do that. structure, the slower the recovery. State. Of course, the ocean is not a great hole into which California can fall, but it is itself land at a somewhat lower elevation with water above it. The motion of plates will not make California sink —western California is mov- ing horizontally along the San Andreas fault and up around the Transverse ranges. Replacement Costs Business Interruption n Shaking Damage to Buildings and Contents n Shaking Damage n Fire Damage to Buildings and Contents n Fire Damage n Highway Damage n Transportation Disruption n Pipeline Damage n Utilities Disruption n Ports Disruption

1 The ShakeOut earthquake will cause many shocks to Southern California’s regional economy. Under- standing and comparing the impact of these shocks is important to recovery planning. When considering the cost of replacing lost buildings, building contents, and infrastructure, fire creates the biggest shock to the economic system, bigger than shaking, fault rupture, landslides, and liquefaction combined. This makes sense, because fire can destroy so completely. However, when considering the length of time that normal business will be interrupted, disruption of utility service creates the biggest shock. This makes sense, because few businesses can function without water or power.

12 Why should I care?

Lifelines and Facilities — The Key to Recovery

Power will go out immediately, everywhere, and restoration times vary. In the most heavily damaged areas, electricity will remain out for weeks or longer. Some residences will suffer broken gas lines when their houses slip from unbolted foundations.

Water will stop flowing in many taps for weeks or months. In many communities, strong ground shaking will break old, brittle water pipes and connectors, and there will be so many breaks that it will prove cheaper and faster to replace the entire conveyance system, rather than hunt and repair every break. The process will be neither cheap nor fast, and communities will compete for repair priority.

Many wastewater pipes are also old and brittle, and run alongside water pipes under the streets. Broken sewer pipes will contaminate broken water pipes, and in some places, tap water will be unsafe to drink for as long as a year.

Telecommunications will be out for at least a day, because of some damage and much overuse. Phone systems will be oversaturated because millions are trying to make calls at once. How cell phone towers are affixed to buildings is not regulated, so towers will be damaged by shaking. Two thirds of the region’s internet lines will be ruptured by the fault.

1 To bounce back quickly from a disaster, Transportation by road and rail will be disrupted by fault rupture and communities need to become resilient. landslides, and take months to repair. Retrofitting of state highway bridges Community resilience depends on how many prevents their collapse, but not those under most local jurisdictions. For individuals, businesses, schools, agencies, and months, getting around the southland will take longer, and travel time delays organizations are prepared. It is a lot like vot- add more than $4 billion to economic losses. ing, where personal decisions and actions can affect everyone: an individual learns about the issues (learns about the earthquake impacts Hospitals in the hardest hit counties of Riverside, San Bernardino, and Los and mitigation strategies), decides how to Angeles will be operating at reduced functionality. At a time when thousands vote (decides which mitigation efforts will best of disaster victims need hospital care, some hospital buildings will be closed protect loved ones and financial security), by structural damage; many others will be unusable because of non-structural then casts a ballot (takes action to increase damage such as broken water pipes and unsecured equipment. preparedness). If enough people vote the same way (get prepared), they will have a winning platform (they will have a resilient community)! Public schools—grades K-12 and community colleges—are protected by the Field Act, legislation that sets special construction and inspection stan- dards. Structurally, public schools will hold up well, although non-structural and contents damage will pose problems. Private schools and universities are not protected by the Field Act and some will suffer both structural and non-structural damage.

The Ports of Los Angeles and Long Beach are important contributors to the region’s economy. They will not suffer much damage from this far-away earth- quake, but their flow of goods will be disrupted for months, as many principal train routes and truck routes are damaged by fault rupture.

13 What should I do? 14 Earthquake Safety The SevenStepsto next steps. what youhavedonetoprepareandtogetherplanyour quakes andtsunamisinSouthernCalifornia.Thendiscuss about whatyou’velearnedinthishandbookearth- talk toyourfamily,friends,neighborsandco-workers is clear—butwhereshouldyoustart?Startbytalking— Preparation isthekeytosurvivingadisaster—thatmuch dollars saved. them, countlesscasualtiescanbeavoidedandmillionsof schools, workplaces,andotherfacilities.Byfollowing recover quickly.Thesestepsshouldalsobefollowedin and yourlovedonessafe,reducepotentialdamage The sevenstepsthatfollowincludeactionstokeepyou survive andrecover. next damagingearthquakecanhelpyouandyourfamilyto is not—eveninaverylargeearthquake.Preparingforthe Earthquakes andtsunamisareinevitablebutthedamage 23 1 18 29 2 3 19 4 22 7 5. Drop, cover, andholdon 5. during anearthquake: SURVIVE Strengthen yourhome 4. Prepare disasterkits 3. Create aplan 2. Secure yourspace 1. before anearthquakeortsunami: PREPARE seven steps. trap. Youcanstarttodaybyfollowingthese don’t prepareatall.Donotfallintothat prospect ofanaturaldisasterand,asresult, Many peopleareoverwhelmedbythemere 7. Follow yourplan 7. Check forinjuriesanddamage 6. after anearthquakeortsunami: RECOVER (page 23) (see illustrationbelowandpage16) 5 6 (page18) (page24)

(page19) (page 20) (page22) 24

What should I do?

STEP 1 STEP 2 STEP 3 Secure your space Create a plan Prepare disaster kits

1 Hang plants in lightweight pots with closed 18 Store fire extinguisher (type ABC) in easily 27 Keep an emergency backpack with copies hooks, well secured to a joist or stud and far accessible location. of important documents near the door to away from windows. 19 Keep several flashlights in easily accessible grab and go. 2 Install strong latches on kitchen cabinets. places around the house. 28 Store emergency food and water supplies 3 Use flexible connections where gas lines meet 20 Keep wrench or turn-off tool in water proof in a dry accessible area. Include first appliances. wrap near gas meter. aid kit, extra cash, portable radio, extra 4 Remove or lock refrigerator wheels, secure 21 Know the location of your main electrical switch batteries, medications and other necessary to studs. (fuse box or circuit breaker). supplies. 5 Secure valuable electronics items such as 22 Have your emergency plan accessible and computers and televisions. discuss with all family members. 6 Keep breakables in low or secure cabinets 23 Know whether you live, work or play in a tsunami STEP 4 with latches. hazard zone. Strengthen your home 7 Move heavy plants and other large items to 24 Obtain a NOAA Weather Radio with the Public floor or low shelves. Alert feature to notify you of 29 Use anchor bolts every 4 to 6 feet to secure 8 Hang mirrors and pictures on closed hooks. tsunamis and other hazards. home to foundation. 9 Secure free-standing woodstove or fireplace 25 Keep flashlight, slippers and gloves next 30 Reinforce brick chimneys insert. to beds. 10 Keep heavy unstable objects away from 26 Keep gas tank at least half full. doors and exit routes. STEPS 5-7 11 Place bed away from windows or items During and after the earthquake that may fall. 12 Secure knick knacks and other small valuables see pages 22–25 with museum putty. 13 Brace overhead light fixtures. 14 Place only light weight/soft items over bed. 15 Secure top-heavy furniture to studs. 16 Secure water heater with metal straps attached to studs. 17 Trim hazardous tree limbs.

30

17 13 28 14 8 15 21 27 26 12 16

20 9 25 11

10

Visit earthquakecountry.org for additional instructions and resources.

LEARN MORE: See the web resources listed on page 32. 15 IDENTIFY POTENTIAL HAZARDS IN YOUR HOME do? 1 AND BEGIN TO FIX THEM. Earthquake safety is more than minimizing damage to buildings. We must also secure the contents of our buildings to reduce the risk to our lives and our pocketbooks.

What should I Several people died and thousands were injured in the Northridge earthquake because of unsecured building contents such as top- pling bookcases. Many billions of dollars were lost due to this type of damage. Much of this damage and injury could have been pre- In the kitchen vented in advance through simple actions to Unsecured cabinet doors fly open during secure buildings and contents. earthquakes, allowing glassware and dishes You should secure anything 1) heavy enough to crash to the floor. Many types of latches to hurt you if it falls on you, or 2) fragile or are available to prevent this: child-proof expensive enough to be a significant loss if latches, hook and eye latches, or positive it falls. In addition to contents within your catch latches designed for boats. Gas appli- living space, also secure items in other areas, ances should have flexible connectors to such as your garage, to reduce damage to reduce the risk of fire. Secure refrigerators vehicles or hazardous material spills. and other major appliances to walls using earthquake appliance straps. There may be simple actions you can do right now that will protect you if an earthquake Objects on open shelves happens tomorrow. START NOW by moving and tabletops furniture such as bookcases away from beds, Collectibles, pottery objects, and lamps can sofas, or other places where people sit or become deadly projectiles. Use either hook sleep. Move heavy objects to lower shelves. and loop fasteners on the table and object, or Then begin to look for other items in your non-damaging adhesives such as earthquake home that may be hazardous in an earthquake. putty, clear quake gel, or microcrystalline wax to secure breakables in place. Move heavy Some of the actions recommended on this items and breakables to lower shelves. page may take a bit longer to complete, but all are relatively simple. Most hardware stores and home centers now carry earthquake safety straps, fasteners, and adhesives.

step 1 PREPARE before the earthquake

16 What should I do?

Hanging objects Furniture Mirrors, framed pictures, and other Secure the tops of all top-heavy furniture, objects should be hung from closed hooks such as bookcases and file cabinets, to a wall. so that they can’t bounce off the walls. Be sure to anchor to the stud, and not just to Pictures and mirrors can also be secured the drywall. Flexible fasteners such as nylon at their corners with earthquake putty. straps allow tall objects to sway without fall- Only soft art such as tapestries should be ing over, reducing the strain on the studs. placed over beds or sofas. Loose shelving can also be secured by apply- ing earthquake putty on each corner bracket. Additional information, including Electronics how-to instructions, is available at Televisions, stereos, computers and micro- In the garage or utility room waves and other electronics are heavy and Items stored in garages and utility rooms can www.earthquakecountry.org costly to replace. They can be secured with fall, causing injuries, damage, and hazardous www.quakeinfo.org flexible nylon straps and buckles for easy spills or leaks. They can also block access to removal and relocation. vehicles and exits. Move flammable or haz- ardous materials to lower shelves or the floor.

Water heater Unsecured water heaters often fall over, rup- turing rigid water and gas connections. If your water heater does not have two straps around it that are screwed into the studs or masonry of the wall, then it is not properly braced. This illustration shows one method of bracing a water heater. Bracing kits are available that make this process simple. Have a plumber install flexible (corrugated) copper water con- nectors, if not already done.

17 Am I at risk? do? Find out if your home or business is at risk to for earthquakes, tsunami’s, and related hazards Earthquakes can occur everywhere in California which means all Californians live with an earthquake risk. In addition to the shaking caused by earthquakes, other things can occur such as landslides, surface fault ruptures and liquefaction—all of which may cause injury or property damage. In addition, 2 some areas within California are vulnerable to tsunamis should an earthquake occur off the coast. Use signs and maps to find out which areas are hazardous. On the open coast areas 100 feet or more in What should I elevation and low areas more than two miles inland are safe. CREATE A DISASTER- PREPAREDNESS PLAN. Visit myhazards.calema.ca.gov to create a map of the hazards you may face in your community, and Will everyone in your household do the right contact your local city our county government for further details on how to be prepared where you live. thing during the violent shaking of a major Then quickly create a plan to reduce your risks. earthquake? Before the next earthquake, get together with your family or housemates to plan now what each person will do before, Plan NOW to be safe during an earthquake: C during and after. Practice “drop, cover, and hold on.” (See Step 5, page 22) Once the earthquake is over, we will have to C Identify safe spots in every room, such as under live with the risk of fire, the potential lack of sturdy desks and tables. C Learn how to protect yourself no matter where utilities and basic services, and the certainty you are when an earthquake strikes. www.dropcoverholdon.org of aftershocks. By planning now, you will be ready. This plan will also be useful for other Plan NOW to respond after an earthquake: Plan NOW to communicate emergencies. C Keep shoes and a flashlight next to each bed. and recover after an earthquake: C Get a fire extinguisher for your home. Your local C Select a safe place outside of your home to meet fire department can train you and your family to your family or housemates after the shaking. use it properly. C Designate an out-of-area contact person who can C Teach everyone in your household to use be called by everyone in the household to relay emergency whistles and/or to knock three times information. Obtain a NOAA Weather Radio with repeatedly if trapped. Rescuers are trained to the Public Alert feature to notify you of Does your community: listen for such sounds. tsunamis and other hazards. C Identify the needs of household members and C Provide all family members with a list of important C have plans to notify you if a tsunami warning is neighbors with special requirements or situations, contact phone numbers. issued? such as use of a wheelchair, walking aids, spe- C Determine where you might live if your home can- C have a designated evacuation zone and posted cial diets, or medication. not be occupied after a disaster. tsunami hazard signs? C Take a Red Cross first aid and cardiopulmonary C Know about the earthquake plan developed by C practice evacuation drills? resuscitation (CPR) training course. Learn who your children’s school or day care. Keep school C conduct tsunami education and awareness else in your neighborhood is trained. emergency release card(s) current. campaigns? C Know the location of utility shutoffs and keep C Keep copies of essential documents, such as needed tools nearby. Know how to turn off the identification, insurance policies, and financial Your community can do all of the above and more gas, water, and electricity to your home. Only turn records, in a secure, waterproof container, and if it has been recognized by the National Weather off the gas if you smell or hear leaking gas. keep with your disaster supplies kits. Include a Service as TsunamiReady. The TsunamiReady C Install smoke alarms and test them monthly. household inventory (a list and photos or video of Change the battery once a year, or when the your belongings). program sets guidelines for adequate tsunami readi- alarm emits a “chirping” sound (low-battery C You may have to take additional steps, especially ness, including the ability to receive and send out signal). if someone has a disability or other access and tsunami warnings, designation of tsunami hazard C Work with your neighbors to identify who has functional needs. Register with your local fire zones and evacuation routes, and outreach pro- skills and resources that will be useful in an department for assistance so needed help can be grams that address both natural and official warn- emergency, and who may need special attention provided. ings. Find out if your community is recognized as (children, elderly, disabled, etc.) C Check with your city or county to see if there is a TsunamiReady at tsunamiready.noaa.gov. If it isn’t, The Great California ShakeOut each October Community Emergency Response Team (CERT) in is an opportunity to practice your plan. Be find out what you can do to encourage your com- your area. If not, ask how to start one. munity to gain this recognition sure to share your plan with people who take care of your children, pets, or home. step 2 PREPARE before the earthquake

18 What should I do? 3 PREPARE DISASTER SUPPLIES KITS.

Personal disaster supplies kits Everyone should have personal disaster supplies kits. Keep them where you spend most of your A special note time, so they can be reached even if your building is badly damaged. The kits will be useful for many emergencies, and especially if you need to evacuate out of a tsunami hazard zone. about children

Keep one kit in your home, another in your car, and a third kit at work. Backpacks or other If earthquakes scare us because we feel out of small bags are best for your disaster supplies kits so you can take them with you if you evacuate. control, think how much more true this must be Include at least the following items: for children, who already must depend on adults for so much of their lives. It is important to spend C Medications, prescription list, copies of medical C Road maps time with children in your care before the next cards, doctor’s name and contact information C List of emergency out-of-area contact earthquake to explain why earthquakes occur. C Medical consent forms for dependents phone numbers Involve them in developing your disaster plan, C First aid kit and handbook C Snack foods, high in water and calories prepare disaster supplies kits, and practice “drop, C Examination gloves (non-latex) C Working flashlight with extra batteries and C Dust mask light bulbs, or light sticks cover, and hold on.” Consider simulating post- C Spare eyeglasses or contact lenses and C Personal hygiene supplies earthquake conditions by going without electricity cleaning solution C Comfort items such as games, crayons, writing or tap water. C Bottled water materials, teddy bears C Whistle (to alert rescuers to your location) C Toiletries and special provisions you need for After the earthquake, remember that children will C Sturdy shoes yourself and others in your family including be under great stress. They may be frightened, C Emergency cash (ATMs might not work) elderly, disabled, small children, and animals. their routine will probably be disrupted, and the Small bills and coins are best. C If you have difficulty communicating, keep a note- aftershocks won’t let them forget the experience. C Copies of personal identification (drivers license, book, pencils, etc. in several locations work ID card, etc.) Adults may need to leave their children in order to deal with the many demands of the emergency, Household disaster supplies kit but this can be devastating to children. Extra contact and support from parents in the early days Electrical, water, transportation, and other vital systems can be disrupted for several days or will pay off later. Whenever possible, include them much longer in some places after a large earthquake. Emergency response agencies and hospitals in the recovery process. could be overwhelmed and unable to provide you with immediate assistance. Providing first aid and having supplies will save lives, will make life more comfortable, and will help you cope after the next earthquake.

In addition to your personal disaster supplies kits, store a household disaster supplies kit in an easily accessible location (in a large watertight container that can be easily moved), with a supply of the following items to last at least 3 days and ideally for 2 weeks:

C Water (minimum one gallon a day for each person C Canned and packaged foods and pet, for drinking, cooking, and sanitation) C Charcoal or gas grill for outdoor cooking and C Wrenches to turn off gas and water supplies matches if needed C Work gloves and protective goggles C Cooking utensils, including a manual can opener C Heavy duty plastic bags for waste, and to serve C Pet food and pet restraints. Include supplies for as tarps, rain ponchos, and other uses seeing eye, hearing, or companion dogs. C Portable radio with extra batteries (or hand C Comfortable, warm clothing including extra socks crank for charging) C Blankets or sleeping bags, and perhaps even C Additional flashlights or light sticks a tent C Non-powered corded phone (if only cordless C Copies of vital documents such as insurance phones are normally used) policies

Use and replace perishable items like water, food, medications and batteries on a yearly basis. Keep special medical or mobility equipment (ventilators, oxygen tanks, extra cane, etc.) where they can be easily reached. step 3 PREPARE before the earthquake

19 Metal bracket Floor do? joist

Rim joist Floor Metal Top plate joist bracket

Top What should I 4 Stud plate Nails

IDENTIFY YOUR BUILDING’S Plywood POTENTIAL WEAKNESSES AND Nails BEGIN TO FIX THEM.

Buildings are designed to withstand the down- Bolt ward pull of gravity, yet earthquakes shake a

building in all directions—up and down, but Sill plate most of all, sideways. There are several common issues that can limit a building’s 1 This cutaway diagram shows how weak cripple walls can be strengthened by properly attached ability to withstand this sideways shaking. plywood sheets. [Illustration credit: San Leandro EQ Retrofit Program]

Additional information, including how-to instructions, is available at www.earthquakecountry.org Common building problems Most houses are not as safe as they could be. Unbraced cripple walls. Homes with a crawl The following presents some common struc- space should have panels of plywood connecting tural problems and how to recognize them. the studs of the short “cripple” walls (see figure). Once you determine if your building has one You or a contractor can strengthen the cripple walls or more of these problems, prioritize how relatively inexpensively. and when to fix them, and get started. Soft first stories. Look for larger openings in the lower floor, such as a garage door or a hillside Inadequate foundations. Look under your house built on stilts. Consult a professional to deter- house at your foundation. If the foundation is dam- mine if your building is adequately braced. aged or built in the “pier and post” style, consult Unreinforced masonry. All masonry (brick a contractor or engineer about replacing it with or block walls) should be reinforced. Some commu- a continuous perimeter foundation. Look for bolts nities have a program for retrofitting buildings made

Don’t be fooled! in the mudsills. They should be no more than 1.8

of unreinforced masonry. If your house has masonry “WE HAVE GOOD meters (6 feet) apart in a single story and 1.2 meters as a structural element consult a structural engineer #4 BUILDING CODES SO (4 feet) apart in a multistory building. Adding bolts WE MUST HAVE GOOD to find what can be done. Inadequately braced to unsecured houses is one of the most important BUILDINGS.” chimneys are a more common problem. Consult a

MYTH steps toward earthquake safety. This can be done professional to determine if your chimney is safe. by a contractor or by someone skilled at home The best building codes in the maintenance. world do nothing for build- ings built before a code was enacted. While the codes have been updated, the older buildings are still in place. Fixing problems in older build- ings—retrofitting—is the responsibility of the building’s owner. step 4 PREPARE before the earthquake

20 What should I do?

Earthquake insurance in California Structural-Safety Quiz If you own your home it is probably your for Single-Family Home or Duplex biggest single asset. You have worked hard to secure your piece of the American Dream by becoming a homeowner. In seconds, your If you live in a single-family home or duplex, the strength of your home dream can become a nightmare when an depends on when it was built, its style of construction, and its location. earthquake strikes and damages your home My score and personal belongings. Even if you follow 1. When was your home built? the steps in this handbook, it is likely your C Before 1960 = 5 points home will still have some level of damage, C 1961–1978 = 3 points and you will need to repair or replace belong- C After 1978 = 1 point ings. One option for managing these potential 2. How tall is your home? costs is to buy earthquake insurance. C 2 or more stories with living area above a garage = 5 points C Split level, on a hillside or gentle slope = 6 points Earthquake insurance in California is typically C 1 story, 3 or more steps up to the front door = 4 points not part of your homeowners insurance pol- C 1 story, less than 3 steps up to the front door = 1 point icy; it is generally a separate policy you can 3. How hard is the ground likely to shake under your home? purchase when buying homeowners insurance. C Portions of Southern California shown as yellow or green All insurance companies that sell residential in color on the shaking hazard map (page 7) = 5 points property insurance in California are required C Elsewhere in Southern California = 7 points by law to offer earthquake insurance to home- TOTAL POINTS owners when the policy is first sold and then If your home scores 13 or more points every two years thereafter. on the quiz, you probably should have an engineer, architect, or contractor The cost of the earthquake policy you are evaluate it unless it has been strength- offered is based on a number of factors, ened in the past few years. including your home’s location, age, construc- tion type, and value. It is up to each home- owner to consider their individual risk factors For those who rent If you live in a mobile home... and then weigh the cost of earthquake cover- age against the benefits that coverage may As a renter, you have less control over the Look under your home. If you only see a offer after a devastating earthquake. structural integrity of your building, but metal or wood “skirt” on the outside with you do control which apartment or house concrete blocks or steel tripods or jacks Many companies issue California Earthquake you rent: supporting your home, you need to have Authority (CEA) insurance policies, which an “engineered tie-down system” or an U Structures made of unreinforced brick or are designed to rebuild your home if it suffers “earthquake-resistant bracing system” block walls can collapse and cause great significant damage from an earthquake. loss of life. (ERBS) installed. An ERBS should have a U Apartment buildings with “tuck-under” label on the bracing that says, “Complies You may purchase a CEA policy only parking space openings can also collapse. with the California Administrative Code, through the CEA’s participating insurers. U Foundation and cripple wall failures can Title 25, Chapter 2, Article 7.5.” A complete list is on the CEA web site at cause expensive damage but less loss of life. U Objects attached to the sides of buildings, www.earthquakeauthority.com, which has an such as staircases, balconies, and decora- online premium calculator. tions, can break off in earthquakes. Contact your homeowners insurance company Ask your landlord these questions: or agent to help you evaluate your earthquake risk factors and then consider whether earth- U What retrofitting has been done on this building? quake insurance is a good choice for you. U Have the water heaters been strapped to the wall studs? U Can I secure furniture to the walls?

21 do? 5

What should I PROTECT YOURSELF DURING EARTHQUAKE SHAKING— DROP, COVER, AND HOLD ON.

The previous pages have concentrated on getting ready for the next earthquake. What should you do during and after earthquakes?

The area near the exterior walls of a building If you are… In a high-rise: Drop, cover, and hold on. is the most dangerous place to be. Windows, Avoid windows and other hazards. Do not use Indoors: Drop, cover, and hold on. facades and architectural details are often the elevators. Do not be surprised if sprinkler systems Drop to the floor, take cover under a sturdy desk first parts of the building to collapse. To stay or fire alarms activate. or table, and hold on to it firmly. Be prepared to away from this danger zone, stay inside if you move with it until the shaking stops. If you are not In a stadium or theater: Stay at your seat are inside and outside if you are outside. near a desk or table, drop to the floor against the and protect your head and neck with your arms. interior wall and protect your head and neck with Don’t try to leave until the shaking is over. Then Learn more about what to do (and what not to your arms. Avoid exterior walls, windows, hanging walk out slowly watching for anything that could do) to protect yourself during earthquakes at objects, mirrors, tall furniture, large appliances, and fall in the aftershocks. kitchen cabinets with heavy objects or glass. Do not www.dropcoverholdon.org. Below a dam: Dams can fail during a major go outside! earthquake. Catastrophic failure is unlikely, but if In bed: If you are in bed, hold on and stay there, you live downstream from a dam, you should know protecting your head with a pillow. You are less flood-zone information and have prepared an evacu- likely to be injured staying where you are. Broken ation plan. glass on the floor has caused injury to those who have rolled to the floor or tried to get to doorways.

In a wheelchair: Lock the wheels once you are in a safe position. If unable to move quickly, stay where you are. Cover your head and neck with your arms. Outdoors: Move to a clear area if you can safely do so; avoid power lines, trees, signs, build- “HEAD FOR THE Don’t be fooled! ings, vehicles, and other hazards. DOORWAY.”

#5 Driving: Pull over to the side of the road, stop, An enduring earthquake and set the parking brake. Avoid overpasses, image of California is a col- bridges, power lines, signs and other hazards. Stay MYTH lapsed adobe home with the inside the vehicle until the shaking is over. If a How will I know if an earthquake is big enough to door frame as the only stand- power line falls on the car, stay inside until a trained cause a tsunami? ing part. From this came our person removes the wire. belief that a doorway is the Get into the habit of COUNTING how long the earth- safest place to be during an quake lasts. If you count 20 seconds or more of earthquake. True—if you live shaking and are in a tsunami hazard zone, evacuate in an old, unreinforced adobe to a safe area as soon as you can safely walk. Even house. In modern houses, if you aren’t in a tsunami zone, counting is a good doorways are no stronger than any other part of the idea—it will help to keep you calm. house. You are safer under a table. step 5 SURVIVE during the earthquake

22 What should I do?

Check for injuries Damaged Electrical Wiring. Shut off power at the main breaker switch if there is any damage UÊ iVŽÊޜÕÀÊvˆÀÃÌÊ>ˆ`ʎˆÌʜÀÊÌ iÊvÀœ˜ÌÊ«>}iÃÊof your telephone book for detailed instructions on first to your house wiring. Leave the power off until the 6 damage is repaired. aid measures. UÊ vÊ>Ê«iÀܘʈÃÊLii`ˆ˜}]Ê«ÕÌÊ`ˆÀiVÌÊ«ÀiÃÃÕÀiʜ˜ÊÌ iÊ Broken Lights and Appliances. Unplug AFTER THE EARTHQUAKE, wound. Use clean gauze or cloth, if available. these as they could start fires when electricity is CHECK FOR INJURIES AND UÊ vÊ>Ê«iÀܘʈÃʘœÌÊLÀi>Ì ˆ˜}]Ê>`“ˆ˜ˆÃÌiÀÊ restored. rescue breathing. DAMAGE Downed Power Lines. If you see downed UÊ vÊ>Ê«iÀÜ˜Ê >ÃʘœÊ«ÕÃi]ÊLi}ˆ˜Ê *,Ê power lines, consider them energized and stay well First take care of your own situation. (cardiopulmonary resuscitation). away from them. Keep others away from them. UÊ œÊ˜œÌʓœÛiÊÃiÀˆœÕÏÞʈ˜ÕÀi`Ê«iÀܘÃÊ՘iÃÃÊ Remember your emergency plans. Never touch downed power lines or any objects in they are in immediate danger of further injury. Aftershocks may cause additional damage contact with them. UÊ œÛiÀʈ˜ÕÀi`Ê«iÀܘÃÊÜˆÌ ÊL>˜ŽiÌÃʜÀÊ>``ˆÌˆœ˜>Ê or items to fall, so get to a safe location. clothing to keep them warm. Fallen Items. Beware of items tumbling off Take your disaster supplies kit. UÊ iÌʓi`ˆV>Ê i«ÊvœÀÊÃiÀˆœÕÃʈ˜ÕÀˆið shelves when you open closet and cupboard doors. UÊ >ÀivՏÞÊV iVŽÊV ˆ`Ài˜ÊœÀÊœÌ iÀÃʘii`ˆ˜}Ê Spills. Use extreme caution. Clean up any spilled If you are trapped by falling items or a special assistance. medicines, drugs, or other non-toxic substances. collapse, protect your mouth, nose, and eyes *œÌi˜Ìˆ>ÞÊ >À“vՏʓ>ÌiÀˆ>ÃÊÃÕV Ê>ÃÊLi>V ]ʏÞi]Ê from dust. If you are bleeding, put pressure Check for damage garden chemicals, and gasoline or other petroleum on the wound and elevate the injured part. Fire. If possible, put out small fires in your home or products should be isolated or covered with an Signal for help with your emergency whistle, neighborhood immediately. Call for help, but don’t absorbent such as dirt or cat litter. When in doubt, leave your home. a cell phone, or knock loudly on solid pieces wait for the fire department. of the building, three times every few min- Gas Leaks. Shut off the main gas valve only if Damaged Masonry. Stay away from chim- neys and walls made of brick or block. They may utes. Rescue personnel will be listening for you suspect a leak because of broken pipes or the odor or sound of leaking natural gas. Don’t turn be weakened and could topple during aftershocks. such sounds. it back on yourself—wait for the gas company to Don’t use a fireplace with a damaged chimney. It check for leaks. The phone book has detailed infor- could start a fire or let poisonous gases into your Once you are safe, help others and check for mation on this topic. home. damage. Protect yourself by wearing sturdy shoes and work gloves, to avoid injury from broken glass and debris. Also wear a dust mask and eye protection.

step 6 RECOVER after the earthquake

Don’t be fooled! “EVERYONE WILL PANIC

EVACUATE if you are in a tsunami hazard zone. DURING THE BIG ONE!”

For a large local earthquake, feeling strong ground shaking may be the only warning you will get that a tsunami #6 is on its way. Use tsunami hazard maps and posted hazard zone signs to identify safe evacuation areas. A common belief is that people always panic and run MYTH > If you are at the beach, move to higher ground immediately–no matter how small the earthquake. around madly during and after > If you are in a tsunami hazard zone and the earthquake is very strong, immediately gather your family earthquakes, creating more members, grab your tsunami disaster kit, and WALK to a safe area. danger for themselves and others. Actually, research > If evacuation is impossible, go to the upper f loor of a sturdy building or climb a tree. This should only be a shows that people usually last resort. take protective actions and > Do not wait for an off icial warning help others both during and after the shaking. Most people STAY WHERE YOU ARE if you are not in a tsunami hazard zone. don’t get too shaken up about You are not at risk of a tsunami. Unnecessary evacuation will put you at risk and hamper the evacuation of being shaken up! people who really need to get away from danger.

23 What should I do? ʈÃÌi˜Ê̜ÊÌ iÊÀ>`ˆœÊvœÀÊÕ«`>ÌiÃʜ˜ÊÌ iÊ >â>À`Ê>˜`ÊÊ €Ê iÛ>VÕ>̈œ˜ÊœvÊVœ>ÃÌ>Ê>Ài>ð Ê >“«iÀÃÊÃ>viÊ>˜`Ê̈“iÞÊ ˜Vœ“ˆ˜}ÊÌÀ>vvʈV Ê /Ã՘>“ˆÃʓœÛiÊv>ÃÌiÀÊÌ >˜Ê>Ê«iÀܘÊV>˜ÊÀ՘°Ê €Ê iÛiÀÊ}œÊ̜ÊÌ iÊVœ>ÃÌÊ̜ÊÜ>ÌV Ê>ÊÌÃ՘>“ˆ°Ê €Ê œÀʏœ˜}iÀ° Ê >«>ÀÌ°Ê/ iÊ`>˜}iÀÊ«iÀˆœ`ʓ>Þʏ>ÃÌÊiˆ} ÌÊ œÕÀÃÊ Ê ˆ˜ÌiÀÛ>ÃÊë>Vi`ʓˆ˜ÕÌiÃÊ̜ÊÌi˜Ãʜvʓˆ˜ÕÌiÃÊ Ê -ÕVViÃÈÛiÊÃÕÀ}iÃÊ܈Ê>ÀÀˆÛiÊ>ÌʈÀÀi}Տ>ÀÊ Ê >À}iÃÌÊÜ>ÛiÃʓ>ÞÊ>ÀÀˆÛiÊ œÕÀÃÊ>vÌiÀÊÌ iÊvʈÀÃÌ° Ê / iÊvʈÀÃÌÊÃÕÀ}iʈÃÊ>“œÃÌʘiÛiÀÊÌ iʏ>À}iÃÌ°Ê/ iÊ €Ê Ì iÊ>Ài>ÊvœÀÊޜÕÊ̜ÊÀiÌÕÀ˜° Ê -Ì>ÞÊ>Ü>ÞÊvÀœ“ÊÌ iÊVœ>ÃÌÊ՘̈ÊœvvʈVˆ>ÃÊÀiœ«i˜Ê €Ê (see Step2,page18) to followtheplanyoupreparedinadvance immediate needsafteranearthquake,continue Once youhavemetyourandfamily’s term effectsoftheearthquakeonyourlife. below tobesafeandminimizethelong- to monthsorlonger.Taketheactionslisted Your recoveryperiodcantakeseveralweeks cover, andholdon. additional damage.Alwaysbereadytodrop, quakes. Somemaybelargeenoughtocause to happenforseveralweeksaftermajorearth- CONTINUETOFOLLOW PREPAREDNESS YOUR vœÀʈ˜ÃÌÀÕV̈œ˜Ãʜ˜ÊÜ >ÌÊ̜Ê`œ° Ê 7 HNSF, WHEN SAFE, . Aftershockswillcontinue DISASTER 24 PLAN. Ê œÊ˜œÌÊi>ÌʜÀÊ`Àˆ˜ŽÊ>˜ÞÌ ˆ˜}ÊvÀœ“Êœ«i˜ÊVœ˜Ì>ˆ˜iÀÃÊ UÊ iVŽÊœ˜ÊÌ iÊVœ˜`ˆÌˆœ˜ÊœvÊޜÕÀʘiˆ} LœÀð UÊ Ê >ÊޜÕÀʜÕ̇œv‡>Ài>ÊVœ˜Ì>VÌ]ÊÌiÊÌ i“ÊޜÕÀÊ UÊ ÊvÊޜÕÀÊÜ>ÌiÀʈÃʜvvʜÀÊ՘Ã>vi]ÊޜÕÊV>˜Ê`Àˆ˜ŽÊvÀœ“Ê UÊ *>ViÊ>Ê« œ˜iÃÊL>VŽÊœ˜ÊÌ iˆÀÊVÀ>`ið UÊ ÊˆÃÌi˜Ê̜ÊޜÕÀÊÀ>`ˆœÊvœÀÊÃ>viÌÞÊ>`ۈÜÀˆiÃ°Ê UÊ vÊ«œÜiÀʈÃʜvv]Ê«>˜Ê“i>ÃÊ̜ÊÕÃiÊÕ«ÊÀivÀˆ}iÀ>Ìi`Ê UÊ Food andwater /ÕÀ˜Êœ˜ÊޜÕÀÊ«œÀÌ>LiʜÀÊV>ÀÊÀ>`ˆœÊvœÀʈ˜vœÀ“>̈œ˜Ê UÊ Be incommunication fire hazardinaftershocks. can releasedeadlycarbonmonoxideorbea gas orcharcoalgrills,generators.These indoors: campstoves,gaslanternsorheaters, motor vehicles,etc.).Neverusethefollowing can createaspark(lightswitches,generators, ate anyelectricalormechanicaldevicethat (lighters, matches,candles,orgrills)oper- are nogasleaks,donotuseopenflames in yourdisasterkits.Untilyouaresurethere disaster planandthesuppliesyouorganized Use theinformationyouputtogetherinyour The firstdaysaftertheearthquake… Ì >ÌÊ>Àiʘi>ÀÊà >ÌÌiÀi`Ê}>Ã𠫜œÃʜÀÊë>𠏈vi‡Ã>ۈ˜}ÊVœ““Õ˜ˆV>̈œ˜Ã° Ûi}iÌ>LiðÊ
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RECOVER after theearthquake

What should I do?

If you cannot stay in your home… If your home is structurally unsafe or threat- ened by a fire or other hazard, you need to evacuate. However, shelters may be over- crowded and initially lack basic services, so -Ìi« 2 do not leave home just because utilities are Ài>ÌiÊ>Ê«>˜° out of service or your home and its contents have suffered moderate damage. -Ìi« 1 -iVÕÀiÊޜÕÀÊë>Vi° If you evacuate, tell a neighbor and your -Ìi« 3 out-of-area contact where you are going. As *Ài«>ÀiÊ soon as possible, set up an alternative mailing `ˆÃ>ÃÌiÀʎˆÌð address with the post office. Take the follow- ing, if possible, when you evacuate: UÊ *iÀܘ>Ê`ˆÃ>ÃÌiÀÊÃÕ««ˆiÃʎˆÌÃÊ UÊ i`ˆV>̈œ˜ÃÊ>˜`ÊiÞiÜi>ÀÊ P R UÊ -Õ««ÞʜvÊÜ>ÌiÀ]Êvœœ`]Ê>˜`ÊØ>VŽÃÊ E >> UÊ >˜ŽiÌÉ«ˆœÜÉ>ˆÀʓ>ÌÌÀiÃÃʜÀÊÏii«ˆ˜}Ê«>`Ê > P UÊ >˜}iʜvÊVœÌ ˆ˜}Ê>˜`Ê>ʍ>VŽiÌÊ in a g A UÊ /œÜiÊ>˜`ÊÜ>à VœÌ Ê a

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R >ÛiÊ>Ê«>˜ÊvœÀÊޜÕÀÊ«iÌÃʈ˜Ê>`Û>˜Vi°®Ê UÊ >À}iʵÕ>˜ÌˆÌˆiÃʜvÊ՘˜iViÃÃ>ÀÞÊVœÌ ˆ˜}Ê -Ìi« 4 œÀÊœÌ iÀÊ«iÀܘ>ÊˆÌi“ÃÊ -ÌÀi˜}Ì i˜Ê UÊ 6>Õ>LiÃÊÌ >Ìʓˆ} ÌÊLiʏœÃÌ]ÊÃ̜i˜]ʜÀÊÌ>ŽiÊÕ«Ê ÞœÕÀÊ œ“i° ˜ii`i`Êë>Vi -Ìi« 7 Once a Presidential Declaration has been œœÜÊޜÕÀÊ «>˜° issued, FEMA may activate the Individuals and Households Program (www.fema.gov/ assistance). This program includes: UÊ œ“i‡Ài«>ˆÀÊV>à Ê}À>˜ÌÃÆÊÌ iʓ>݈“Õ“Êi`iÀ>Ê -Ìi« 6 -Ìi« 5 }À>˜ÌÊ>Û>ˆ>LiÊ­>ÃʜvÊÓääx®ÊˆÃÊfÓÈ]ÓääÊ iVŽÊvœÀʈ˜ÕÀˆiÃÊ Àœ«]ÊVœÛiÀ]Ê UÊ œÕȘ}Ê
ÃÈÃÌ>˜Viʈ˜ÊÌ iÊvœÀ“ÊœvÊÀiˆ“LÕÀÃi“i˜ÌÊ >˜`Ê`>“>}i° >˜`Ê œ`ʜ˜° vœÀÊà œÀ̇ÌiÀ“ʏœ`}ˆ˜}Ê>ÌÊ>Ê œÌiÊ UÊ ,i˜Ì>Ê>ÃÈÃÌ>˜ViÊvœÀÊ>Ãʏœ˜}Ê>ÃÊ£nʓœ˜Ì Ãʈ˜ÊÌ iÊ vœÀ“ÊœvÊV>à ʫ>ޓi˜ÌÊ UÊ vʘœÊœÌ iÀÊ œÕȘ}ʈÃÊ>Û>ˆ>Li]Ê
ʓ>ÞÊ«Àœ‡ ۈ`iʓœLˆiÊ œ“iÃʜÀÊœÌ iÀÊÌi“«œÀ>ÀÞÊ œÕȘ} Once you have recovered from the earthquake, }œÊL>VŽÊÌœÊ -Ìi«Ê£Ê>˜`Ê`œÊÌ iÊÌ ˆ˜}ÃÊޜÕÊ`ˆ`ʘœÌÊ`œÊLivœÀi]ʜÀÊ`œÊÌ i“Ê “œÀiÊÌ œÀœÕ} Þ°Êi>À˜ÊvÀœ“ÊÜ >ÌÊ >««i˜i`Ê`ÕÀˆ˜}ÊÌ iÊ i>ÀÌ µÕ>ŽiÊÜÊޜÕÊ܈ÊLiÊÃ>viÀÊ>˜`ÊÀiVœÛiÀʓœÀiʵՈVŽÞÊ ˜iÝÌÊ̈“i°

25 Earthquake Basics EARTHQUAKES AND FAULTS What is an earthquake? Epicenter, hypocenter, aftershock, foreshock, fault, An earthquake is caused by a sudden slip on fault plane, seismograph, P-waves, magnitude, inten- a fault, much like what happens when you sity, peak acceleration, amplification... snap your fingers. Before the snap, you push your fingers together and sideways. Because know? We hear them. After big earthquakes, we say them. you are pushing them together, friction keeps But what do these terms mean? What do they mean them from moving to the side. When you push sideways hard enough to overcome this fric- for what we felt and what we will feel the next time? tion, your fingers move suddenly, releasing Do we really understand what seismologists are energy in the form of sound waves that set the saying? air vibrating and travel from your hand to your ear, where you hear the snap. This section describes how earthquakes happen The same process goes on in an earthquake. and how they are measured. It also explains why the Stresses in the earth’s outer layer push the same earthquake can shake one area differently than sides of the fault together. The friction across another area. It finishes with information we expect the surface of the fault holds the rocks together

What should I to learn after future earthquakes. so they do not slip immediately when pushed . sideways. Eventually enough stress builds up and the rocks slip suddenly, releasing energy in waves that travel through the rock to cause the shaking that we feel during an earthquake.

Just as you snap your fingers with the whole area of your fingertip and thumb, earthquakes happen over an area of the fault, called the rupture surface. However, unlike your fingers, the whole fault plane does not slip at once. The rupture begins at a point on the fault plane called the hypocenter, a point usually deep rupture surface down on the fault. The epicenter is the point on the surface directly above the hypocenter. hypocenter The rupture keeps spreading until something stops it (exactly how this happens is a hot

fault plane research topic in seismology).

fault line epicenter

hypocenter

26 What should I know?

How do we know it’s an aftershock? Foreshocks How do we study faults? mainshock occurs Sometimes what we think is a mainshock is followed by a larger earthquake. Then the Surface features that have been broken and original earthquake is considered a foreshock. offset by the movement of faults are used to these are aftershocks The chance of this happening dies off quickly determine how fast the faults move and thus with time just like aftershocks. After three how often earthquakes are likely to occur. days the risk is almost gone. For example, a streambed that crosses the

Sometimes, the chance that an event is a fore- San Andreas fault near Los Angeles is now shock seems higher than average—usually offset 83 meters (91 yards) from its original because of its proximity to a major fault. The course. The sediments in the abandoned

Number of earthquakes in the region of the mainshock California Emergency Management Agency streambed are about 2,500 years old. If we Year will then issue an advisory based on scientists’ assume movement on the San Andreas has recommendations. These are the only officially cut off that streambed within the last 2,500 Aftershocks recognized short-term “predictions.” years, then the average slip rate on the Part of living with earthquakes is living with fault is 33 millimeters (1.3 inches) per year. What is a fault? aftershocks. Earthquakes come in clusters. This does not mean the fault slips 33 mil- In any earthquake cluster, the largest one is Earthquakes occur on faults. A fault is a thin limeters each year. Rather, it stores up 33 called the mainshock; anything before it is a zone of crushed rock separating blocks of the millimeters of slip each year to be released in foreshock, and anything after it is an after- earth’s crust. When an earthquake occurs on infrequent earthquakes. The last earthquake shock. one of these faults, the rock on one side of offset the streambed another 5 meters the fault slips with respect to the other. Faults Aftershocks are earthquakes that usually (16 feet). If we assume that all earthquakes can be centimeters to thousands of kilometers occur near the mainshock. The stress on the have 5 meters (5000 millimeters) of slip, we long. The fault surface can be vertical, hori- mainshock’s fault changes during the main- will have earthquakes on average every 150 zontal, or at some angle to the surface of the shock and most of the aftershocks occur on years: 5000 millimeters divided by 33 millimeters earth. Faults can extend deep into the earth the same fault. Sometimes the change in per year equals 150 years. This does not mean and may or may not extend up to the earth’s stress is great enough to trigger aftershocks on the earthquakes will be exactly 150 years apart. surface. nearby faults as well. While the San Andreas fault has averaged How do we know a fault exists? 150 years between events, earthquakes have An earthquake large enough to cause damage occurred as few as 45 years and as many as will probably produce several felt aftershocks UÊ *>ÃÌÊv>ՏÌʓœÛi“i˜ÌÊ >ÃÊLÀœÕ} ÌÊ̜}iÌ iÀÊÀœVŽÃÊ 300 years apart. within the first hour. The rate of aftershocks that used to be farther apart; - dies off quickly. The day after the mainshock UÊ >ÀÌ µÕ>ŽiÃʜ˜ÊÌ iÊv>ՏÌÊ >ÛiʏivÌÊÃÕÀv>ViÊiۈ dence, such as surface ruptures or fault scarps has about half the aftershocks of the first day. >ÀÀˆâœÊ*>ˆ˜Ê >̈œ˜>Ê œ˜Õ“i˜ÌÊ>œ˜}Ê (cliffs made by earthquakes); the San Andreas fault Ten days after the mainshock there are only UÊ >ÀÌ µÕ>ŽiÃÊÀiVœÀ`i`ÊLÞÊÃiˆÃ“œ}À>« ˆVÊ a tenth the number of aftershocks. An earth- networks are mapped and indicate the quake will be called an aftershock as long as location of a fault. the rate of earthquakes is higher than it was before the mainshock. For big earthquakes, Some faults have not shown these signs and this might go on for decades. we will not know they are there until they Bigger earthquakes have more and larger produce a large earthquake. Several damaging aftershocks. The bigger the mainshock, the earthquakes in California have occurred on bigger the largest aftershock, on average, faults that were previously unknown. though there are many more small aftershocks than large ones. Also, just as smaller earth- quakes can continue to occur for many years after a mainshock, there is still a chance for a large aftershock long after an earthquake.

LEARN MORE: See the web resources listed on page 32. 27 LOCATING AND Now computers determine this information MEASURING EARTHQUAKES automatically within minutes. Within a few more hours the shape and location of the know? Where and when was the earthquake? entire portion of the fault that moved can be Earthquakes are recorded by a seismic net- calculated. work. Each seismic station in the network measures the movement of the ground at that We name earthquakes after map locations site. In an earthquake, the slip of a block of near epicenters to have a convenient way to rock over another releases energy that makes refer to them, but this can be misleading.

What should I the ground vibrate. That vibration pushes We define the epicenter of an earthquake the adjoining piece of ground, causing it to with the latitude and longitude of a point, but vibrate, and thus the energy travels out from the earthquake is bigger than that point. The the earthquake in a wave. As the wave passes fault’s rupture surface can be hundreds of by a seismic station, that piece of ground kilometers long and several kilometers wide, and even the epicenter can only be determined

Don’t be fooled! vibrates and this vibration is recorded. “IT’S HOT AND DRY — within a few tenths of a kilometer. Therefore, EARTHQUAKE WEATHER!” #7 Earthquakes produce two main types of waves giving the location of an earthquake in terms Many people believe that —the P-wave (a compressional wave), and the of city streets is like giving the location of MYTH earthquakes are more com- S-wave (a shear wave). The S-wave is slower your city by the address of City Hall. mon in certain kinds of but larger than the P-wave and does most of weather. In fact, no correla- the damage. Scientists have used knowledge How big was the earthquake? tion with weather has been found. Earthquakes begin of the differences between these and other Why do scientists have problems coming up many kilometers below the seismic waves to learn a great deal about the with a simple answer to this simple question? region affected by surface interior of the earth. Many people have felt this frustration after weather. People tend to earthquakes, as seismologists often seem to notice earthquakes that fit the Knowing how fast seismic waves travel pattern and forget the ones contradict one another. In fact, earthquakes through the earth, seismologists can calculate that don’t. Also, every region are very complex. Measuring their size is the time when the earthquake occurred and of the world has a story about something like trying to determine the “size” earthquake weather, but the its location by comparing the times when of an abstract modern sculpture with only one type of weather is whatever shaking was recorded at several stations. This they had for their most memo- use of a tape measure. Which dimension do process used to take almost an hour when rable earthquake. you measure? done manually. Magnitude is the most common way of describing an earthquake’s size. In the 1930s, Beno Gutenberg and Charles Richter at the California Institute of Technology developed a method to describe all sizes of earthquakes using a small range of numbers. Using record- ings from seismographs, they measured how fast the ground moved at a set distance from earthquakes. If the maximum acceleration of the ground in one earthquake is 10 times the seconds maximum acceleration in another earthquake, then the first earthquake is said to be one 1 These seismograms show how the ground moved at four seismic stations during an earth- unit of magnitude larger than the second. The quake. The time when ground starts shaking Richter Scale, as it became known, is not a is the arrival of the P-wave. The ground starts device, but the range of numbers used to shaking sooner and shakes more at sites nearer the earthquake. compare earthquakes.

28 What should I know?

A longer fault can produce a bigger earthquake that lasts a longer time. A magnitude 6.0 earthquake has about 32 times more energy than a magnitude 5.0 Magnitude Date Location Rupture Length Duration and about 1,000 times more energy than a (kilometers) (seconds) magnitude 4.0 earthquake. This does not 9.1 December 26, 2004 Sumatra, Indonesia 1200 500 mean there will be 1,000 times more shaking 7.9 January 9, 1857 Fort Tejon, CA 360 130 at your home. A bigger earthquake will last 7.9 May 12, 2008 Sichuan, China 300 120 longer and release its energy over a much 7.8 April 18, 1906 San Francisco, CA 400 110 larger area. 7.3 June 28, 1992 Landers, CA 70 24 7.3 August 17, 1959 Hebgen Lake , MT 44 12 Seismologists have since developed a new 7.0 October 17, 1989 Loma Prieta, CA 40 7 measurement of earthquake size, called 7.0 October 28, 1983 Borah Peak, ID 34 9 moment magnitude. Moment is a physical 6.8 February 28, 2001 Nisqually, WA 20 6 quantity more closely related to the total 6.7 January 17, 1994 Northridge, CA 14 7 energy released in the earthquake than Richter 6.4 March 10, 1933 Long Beach, CA 15 5 magnitude. It can be estimated by geologists 5.9 October 1, 1987 Whittier Narrows, CA 6 3 examining the geometry of a fault in the field 5.4 July 29, 2008 Chino Hills, CA 5 1 or by seismologists analyzing a seismogram. Because the units of moment are very large, it has been converted to the more familiar range of magnitude values for communication to the public.

Moment magnitude has many advantages over other magnitude scales. First, all earthquakes can be compared on the same scale. (Richter magnitude is only precise for earthquakes of a certain size and distance from a seismometer.) Second, because it can be determined either instrumentally or from geology, it can be used to measure old earthquakes and compare them to instrumentally recorded earthquakes. Third, by estimating how large a section of fault will likely move in the future, the magni- tude of that earthquake can be calculated So. Cal Network image to come with confidence.

Who monitors California’s earthquakes? (Margaret) Earthquake monitoring for California is done by the California Integrated Seismic km Network (CISN), a partnership among the 0 50 U.S. Geological Survey (USGS), University of California Berkeley, Caltech, the California

Geological Survey, and the Governor’s Office 1 The Southern California Seismic Network (SCSN) records data from more than 370 seismic of Emergency Services. CISN is part of a stations. Each station records seismic waves from both near and distant earthquakes. All the data are transmitted automatically to Caltech/USGS in Pasadena for processing and distribution of USGS national seismic monitoring program information such as epicenters, magnitudes, and ShakeMaps. The SCSN is also part of the California called the Advanced National Seismic System Integrated Seismic Network (CISN) that coordinates earthquake monitoring statewide. The symbols (ANSS). For more information go to: indicate different types of seismic stations. www.cisn.org/ or www.anss.org/.

29 What should I know? magnitude, distance,andlocalsoilconditions. quake iscontrolledbythreemainfactors: with onenumber.Whatyoufeelinanearth- jerky orrolling—andisnotdescribable very complex—hardorgentle,longshort, sure oftheshakingyoufeel.Whatfeelis produced byanearthquakeandisnotamea- Magnitude isameasurementoftheenergy EARTHQUAKE SHAKING M6.7 NorthridgeEarthquake 1994 M6.8 NisquallyEarthquake 2001 1 at least50kilometers(30miles)away fromthefault. Northridge earthquake.Thereforeevery housewas much deeperthanthefaultthatmoved inthe reason isthatthesectionoffault movedwas scale, theresultingdamagewasfar less. One than theNorthridgeearthquakeonmagnitude though theNisquallyearthquakewasslightlylarger affects thelevelofshakingexperienced.Even esting exampleofhowdistancefromanearthquake (M6.7) earthquakesshownaboveprovideaninter-

The 2001Nisqually(M6.8)and1994Northridge

30 minutes. so youwouldhavefeltshakingforseveral two minutesforthatlengthoffaulttorupture, 3 kilometers(2miles)persecond,ittook kilometers (220miles)ofthefault.At Andreas faultin1857rupturedalmost360 The magnitude7.8earthquakeontheSan bounce andechowithintheearth. because somewavesreachyouafterthey might continuetofeelshakingforlonger fault isoverinafewseconds,althoughyou 5 event,theactualprocessofrupturing shown onthepreviouspage.Foramagnitude The actualdurationsof15earthquakesare bigger earthquakesthathavelongerdurations. gives offshaking,solongerfaultsproduce ing. Everypointcrossedbytherupturefront fault, producingwavesallthetimeitismov- from theretherupturefronttravelsalong An earthquakebeginsatthehypocenter,and a longerperiodoftime. release theirenergyoveralargerareaandfor from asmallone.Biggerearthquakesalso ing fromahighermagnitudeearthquakethan Typically youwillfeelmoreintenseshak- Magnitude depend solelyonhowharditisshaken.In The amountofdamagetoabuildingdoesnot you willfeelarollingmotion. higher frequencieswillhavediedawayand quake andfeel“jolted.”Fartheraway,the ence alltheshakingproducedbyearth- If youarenearanearthquake,willexperi- with distancethandohigh-frequencywaves. Low-frequency wavesdiminishlessrapidly shaking islessintensefartherfromthefault. they travelthroughtheground,soearthquake Earthquake wavesdiminishinintensityas Distance level ofshakinginthenearbymountains. times greateratasiteinthebasinthan earthquake intheregioncanbe5ormore kilometers (6miles)thick.Shakingfroman basin wheresedimentscanbeasmuch10 by thicksediment—suchastheLosAngeles The samefactorsalsoapplytoareascovered experienced significantshaking. However, somesitesonlandfillorsoftsoils of theBayAreaescapedseriousdamage. ters (60miles)fromSanFrancisco,andmost earthquake. Thatearthquakewas100kilome- San Franciscoduringthe1989LomaPrieta of amplificationwasintheMarinadistrict earthquake. Anextremeexampleforthistype hard rockatthesamedistancefrom soft, loosesoilmayshakemoreintenselythan waves slowdownbutgetbigger.Hencea earthquake. Passingfromrocktosoil,seismic Soils cangreatlyamplifytheshakinginan Local soilconditions distances. the largestearthquakes,evenatconsiderable lower frequenciesandwillbeaffectedby high-rises andbridgesaredamagedmoreby severely damaged.Largerstructuressuchas they mustbeclosetothehypocenter damaged morebyhigherfrequencies,so general, smallerbuildingssuchashousesare This iscalleddirectivity. from thefaultbutinoppositedirection. more shakingthanasiteatthesamedistance that alocationindirectionwillreceive focuses energyinthedirectionitismovingso earthquake rupturemovesalongthefault,it the wavesindifferentdirections.When movement canchangethecharacteristicsof orientation ofthefaultanddirection directions fromtherupturesurface; Earthquake wavesdonottravelevenlyinall Several otherfactorscanaffectshaking. P.S. What should I know?

Did You Feel It? ShakeMap Community Internet Intensity Map — 1994 Northridge earthquake Instrumental Intensity Map — 1994 Northridge earthquake

93534

93532

PALMDALE 93551

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CASTAIC 91390 93543

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93 91354

91351

91350 91387 91355

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93060 91381 91321 91342

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93066 91344 93063 91311 91340 93004 93065 91042 91326

91345 91040 NORTHRIDGE91331 91330 91324 91343 91325 91214 93010 91352 91304 91402 91011

91360 91306 91020 93012 91307 91605 91335 91405 91504 91501 91303 91406 91208 91001 91362 91606 91377 91207 91367 91411 91401 91505 91502 91506 91201 91601 91202 91104 91024 91316 91607 PASADENA91103 91016 91206 91107 93033 91364 91356 91203 91436 91602 91423 91361 91403 91101 91010 91320 91604 91608 91105 91106 . 91301 91204 91205 90041 91006 91702 90068 91007 90027 91302 91108 90042 91775 90039 93042 90065 91030 90077 90046 91780 90290 90210 90028 91706 91722 90069 90038 90029 91801 91776 90049 9 90272 90026 90031 90032 90004 91803 90048 91732 90095 LOS90036 ANGELES 91790 90265 90024 90211 90020 90012 91770 90212 90010 90057 917 90067 90005 90035 90017 91754 90019 90006 90033 91755 90025 90013 90063 91733 90263 90015 90402 90064 90403 90034 90016 90007 91744 90404 90022 90232 90023 90401 90640 90405 90008 90011 90037 90601 90066 91745 SANTA MONICA 90291 90230 90056 90043 90270 90660

90292 90255 90606 91748 90302 90001 90201 90602

90301 90240 90045 90044 90293 90002 90605 90280 90603 90241 90631 90303 90670 90604 90262 90242 90245 90250 90650 90249 90638 92835 90723 90247 90266 90260 90706

90248 90220 92833 9283 90278 90621 90504 90703 92832 90254 90805 90746

90623 90712 90713 90620 92801 90503 90715 90501 90502 90277 90807 92805 90745 90808 90630 92804

90505 92802 90806 90680 90710 90815 km 90717 90720 92841 90804 92840 90744 90813 90274 90814 92844 90803 92843 90802 90275 90740 92683 92703 0 10 20 30 92655 90731 90732

92647 92649 92704 90742 PERCEIVED 5048 responses in 627 ZIP areas. Max intensity: IX 92708 SHAKING Not felt Weak Light Moderate Strong Very strong Severe Violent Extreme 92648 POTENTIAL DAMAGE none none none Very light Light Moderate Moderate/Heavy Heavy Very Heavy INTENSITY I II-III IV V VI VII VIII IX X+ PEAK ACC.(%g) <.17 .17-1.4 1.4-3.9 3.9-9.2 9.2-18 18-34 34-65 65-124 >124 SHAKING Not felt Weak Light Moderate Strong Very strong Severe Violent Extreme PEAK VEL.(cm/s) <0.1 0.1-1.1 1.1-3.4 3.4-8.1 8.1-16 16-31 31-60 60-116 >116

DAMAGE none none none Very light Light Moderate Moderate/Heavy Heavy Very Heavy INSTRUMENTAL INTENSITY I II-III IV V VI VII VIII IX X+

ONLINE EARTHQUAKE INFORMATION

After an earthquake, knowing more about “Did You Feel It?” — Tell us what “ShakeMap” — Within 5 to 10 min- what just happened can reduce fears and help you felt! Personal experiences of the effects utes of most felt earthquakes (magnitude you understand what to expect next. Online of an earthquake are very valuable to 3.5 and greater) in Southern California, a earthquake information products include: scientists. When you have felt a quake, “ShakeMap” is posted on the Web. This please report your observations by using a map shows the range of shaking intensi- Recent earthquakes map — Within quick survey found on the U.S. Geological ties across a region. Every quake has 1 to 2 minutes of an earthquake, its location Survey “Did You Feel It?” Web site at only a single magnitude, but it produces a and magnitude are available at several earthquake.usgs.gov/eqcenter/dyfi.php. range of shaking intensity values over the Web sites, including data.scec.org and area in which it is felt. earthquakes.usgs.gov. When you fill out this online survey, your observations of actual damage and shaking ShakeMaps use data from seismic are combined with those of thousands of instruments to provide a rapid picture of other people. The quake’s shaking intensities, where the strongest shaking occurred. derived from these observations, are displayed These maps help to identify areas where by ZIP code on a “Community Internet a quake’s impact is greatest and are Intensity Map.” used by emergency managers to speed disaster response. ShakeMaps are available at www.cisn.org/shakemap

Last Hour or earthquake.usgs.gov/shakemap.

Last Day

Last Week

Recent Earthquake Map 5:30 am, January 17, 1994 (one hour after the Northridge earthquake)

31 What should I know? What should I do? Why should I care? Did YouFeelIt?–reportit!:earthquake.usgs.gov/eqcenter/dyfi.php Southern CaliforniaShakeMaps:www.cisn.org/shakemap Southern Californiaclickablefaultmap:www.data.scec.org/faults/faultmap.html Southern CaliforniaEarthquakeDataCenter:www.data.scec.org Southern CaliforniaEarthquakeCenter:www.scec.org California GeologicalSurvey:www.consrv.ca.gov/cgs United StatesGeologicalSurveyEarthquakeHazardsProgram:earthquake.usgs.gov What shouldIknow? “Step 1”ingreaterdetail:www.quakeinfo.org Federal EmergencyManagementAgency:www.fema.gov Emergency SurvivalProgram(ESP):www.espfocus.org California SeismicSafetyCommission:www.seismic.ca.gov California EarthquakeAuthority:www.earthquakeauthority.com California EmergencyManagementAgency:www.calema.ca.gov American RedCross:www.redcross.org www.ShakeOut.orgwww.dropcoverholdon.orgwww.terremotos.org Earthquake CountryAlliance:www.earthquakecountry.org What shouldIdo? Recent EarthquakesinSouthernCalifornia:www.data.scec.org/recenteqs.html Historic EarthquakesinSouthernCaliforniaclickablemap:www.data.scec.org/clickmap.html The ShakeOutEarthquakeScenario:urbanearth.usgs.gov/scenario08 LandslideandLiquefactionMaps:gmw.consrv.ca.gov/shmp TsunamiHazards:tsunami.ca.gov SeismicShakingHazardMaps:www.consrv.ca.gov/CGS/rghm/psha/pga.htm California GeologicalSurvey California EarthquakeForecast:www.scec.org/ucerf Why shouldIcare? www.earthquakecountry.org and othersupplementaldocuments,areallavailableat: multiple languages,the Answers formanyofyourquestions,onlineversionsthishandbookin Additional supportprovidedby: (Page 14) (Page4) (Page26) Seven StepstoanEarthquakeResilientBusiness