Putting Down Roots in Earthquake Country

Putting down roots in earthquake country

Spring 2007 edition

Developed and distributed by

and many other organizations (see page 2) Introduction headquartered attheUniversityofSouthernCalifornia. Science FoundationandtheUnitedStatesGeologicalSurvey, SCEC isaresearchconsortiumsupportedbytheNational (SCEC). Reproductionbypermissiononly. Copyright 2007,SouthernCaliforniaEarthquakeCenter “Every day is earthquake season in California” in season earthquake is day “Every Goltz; Emergency Services: Sylvester, DougBausch,JeffreyLusk; David Wald, LisaWald; Kenneth Hudnut,KenRukstales,MichaelRymer, BobSimpson, Marquis, SuzannePerry, GlennSong,BrionVibber; Contributors: edition) andJillAndrews,SCEC(first 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: with permission. mark oftheCaliforniaEarthquakeAuthorityandisused Los Angeles: American RedCross: Insurance InformationNetworkofCalifornia: Turner; Charles Real; Vikki Appel,EgillHauksson,MargaretVinci; Plesch, JohnShaw; Zimmerman (p.14,16,18, 19). Punchstock (p.17,21);JereSmith(cover, p.2,3,32);andRobert (p. 16,19,29);StephanieLangley(p.4,6,10, 14, 19,20,26); Todd Connor(p.14–15);DaleGlasgow24); MinJaeHong Illustrators: Elizabeth Burrill Design: been adoptedinthisSouthernCaliforniaedition. Bay Regionversionofthishandbook,manywhichnowhave Alliance Special thankstomembersofthe Earthquake CountryAlliance Brian Lowe,JeffPrimes;andmanyother 2 California GeologicalSurvey: California EarthquakeAuthority: Denton DesignAssociates:MargiS.Denton, Lucile M.Jones,USGSandMarkBenthien,SCEC for improvementsimplementedintheSanFrancisco Mark BenthienandRobertdeGroot,SCEC(second The suggestionsandillustrationsincludedinthis Fuel CreativeGroup(p.13);DanielClark18); Joyce Harris,PhyllisTan, LarryCollins; California SeismicSafetyCommission: SCEC (USC): KFWB: Peggy Brutsche,RockyLopes; Greg Renick,DeborahSteffen,James FEMA: Ilene Cooper, ThomasHenyey, John Jack Popejoy; Hassaan Sughayer, Dennis 1906 EarthquakeCentennial Jerry Treiman, ChrisWills, California Officeof Nancy Kinkaid; members ofthe Trevco: Harvard: Candy Miller; is aservice Dean Reese, USGS: County of Caltech: Andreas Fred

Why should I care? 10 8 6 4 Southern California Southern California Other earthquake-relatedhazardsin Earthquake shakingpotentialinSouthernCalifornia Southern Californiafaults Southern Californiaearthquakes is Earthquake Country should Southern California,whatweshould This handbookprovidesinformationaboutwhyweshould Southern Californiaisearthquakecountry, andeverydayisearthquakeseason. damaging earthquakes.SomemayhappenbeforethenextmajorSanAndreasearthquake. There arehundredsofotherfaultsthroughoutSouthernCaliforniathatcouldalsocause heavily damaged. lifetime. Whenitdoes,allofSouthernCaliforniawillbeshakenandmanyareasmay 1690). Anothermajorearthquakeislikelytohappenonthissectionofthefaultwithinour Valley totheSaltonSea,over300yearshavepassedsincelastmajorearthquake(around Further southalongtheSanAndreasfault,fromBernardinothroughCoachella so therewasverylittledamage. rupturing thefaultfromCentralCaliforniatoSanBernardino.Fewpeoplelivedinarea, California, thelastmajorearthquakeonSanAndreasfaultwas150yearsago(1857), 1906. Over3,000peoplewerekilledand225,000lefthomeless.InSouthern Andreas earthquake.InNorthernCalifornia,thelastmajorearthquakewas100yearsagoin famous faults—theSanAndreas.However, fewCalifornianshaveexperiencedamajorSan Generations ofCalifornianshavebeen"puttingdownroots"alongonetheworld'smost What should I do? know 22 21 20 19 18 17 16 14 12 to EarthquakeSafety The SevenSteps earthquakes inCalifornia Reducing thecostsof disaster-preparedness plan. #7:Whensafe,continuetofollowyour STEP and damage. #6:Aftertheearthquake,checkforinjuries STEP drop, cover, andholdon. #5:Protectyourselfduringearthquakeshaking— STEP weaknesses andbegintofixthem. #4:Identifyyourbuilding’s potential STEP #3:Preparedisastersupplieskits. STEP #2:Createadisaster-preparedness plan. STEP begin tofixthem. #1:Identifypotentialhazardsinyourhomeand STEP The sevenstepstoearthquakesafety about earthquakebasics. do to besafeandreducedamage,alsowhatwe care What should I know? about earthquakesin 32 The ResourceMine 30 28 26 25 24 Earthquake Basics Web resources Information availableafterearthquakes Earthquake shaking Locating andmeasuringearthquakes Faults Earthquakes 3 Introduction SOUTHERN CALIFORNIA IS EARTHQUAKE COUNTRY We know that the San Andreas fault produces large earthquakes and that many other faults are also hazardous. However, it is often difficult to understand

care? how to incorporate this information into our lives. Should we care only if we live near the San Andreas fault? Is every place just as dangerous? This section describes where and how often earthquakes happen in Southern California. It also explains how earthquakes will shake the ground and cause other hazards such as liquefaction and landslides. Why should I

“BIG EARTHQUAKES Don’t be fooled! Don’t ALWAYS HAPPEN IN THE EARLY MORNING.” #1

This myth may be so common

MYTH because we want it to be true. Several recent damaging SOUTHERN CALIFORNIA What does it mean? earthquakes have been in the EARTHQUAKES early morning, so many people To become familiar Southern California has thousands of earth- believe that all big earth- with earthquake quakes every year. A few are damaging, but quakes happen then. In fact, vocabulary, you may earthquakes occur at all times want to read the most are not even felt. However, almost none of day. The 1933 Long Beach “What Should I Know” are on the San Andreas fault. The last signifi- earthquake was at 5:54 pm section first. cant earthquake on the Southern California and the 1940 Imperial Valley stretch of this fault was in 1857. It is still event was at 8:37 pm. More storing energy for some future earthquake. recently, the 1992 Joshua Tree Other faults produce most of our earthquakes. earthquake was at 9:50 pm and the 2003 San Simeon The Southern California Seismic Network event was at 11:15 am. It is (operated jointly by the U.S. Geological easy to notice the earth- Survey and the California Institute of quakes that fit the pattern and forget the ones that don’t. Technology) recorded several hundred

4 Why should I care?

Earthquakes plotted using data from the Southern California Seismic Network. Significant earthquakes are numbered according to the table below.

thousand earthquakes greater than magnitude Desert and the 1952 magnitude 7.5 Kern Significant Southern California earthquakes since 1933 1 in Southern California between 1981 and County earthquake near Bakersfield. Date Time (local) Location Magnitude 1. 03.10.1933 5:54 pm Long Beach 6.4 2003. The epicenters of these earthquakes are 2. 03.25.1937 8:49 am San Jacinto 6.0 shown by the dark blue dots on the map of By comparing this map with the fault map on 3. 05.18.1940 8:37 pm Imperial Valley 6.9 4. 10.21.1942 9:30 am Fish Creek Mountains 6.6 Southern California on this page. The colored the next page, we can see that there are very 5. 03.15.1946 5:49 am Walker Pass 6.0 few small earthquakes along many of the 6. 04.10.1947 7:58 am Manix 6.5 circles are earthquakes larger than magnitude 7. 12.04.1948 3:43 pm Desert Hot Springs 6.0 major faults, including the San Andreas, 8. 07.21.1952 3:52 am Kern County 7.5 4 since 1932, with the size of the circle 9. 11.21.1952 11:46 pm Bryson 6.2 increasing with magnitude. Small earth- Garlock, and Elsinore fault. Other major 10. 03.19.1954 1:54 am Arroyo Salada 6.4 faults, such as the San Jacinto fault, have both 11. 04.09.1968 6:29 pm Borrego Mountain 6.5 quakes are much more common — the map 12. 02.09.1971 6:01 am San Fernando 6.6 small and large earthquakes. This shows how 13. 10.15.1979 4:54 pm Imperial Valley 6.4 shows 360,000 earthquakes smaller than 14. 07.08.1986 2:21 am North Palm Springs 5.9 magnitude 4 in 22 years, but less than 1600 difficult it can be to predict future earth- 15. 10.01.1987 7:42 am Whittier Narrows 5.9 quakes from patterns of earthquakes. 16. 11.23.1987 5:54 pm Elmore Ranch 6.2 earthquakes above magnitude 4 in 70 years. 17. 11.24.1987 5:15 am Superstition Hills 6.6 18. 04.22.1992 9:50 pm Joshua Tree 6.1 The largest earthquakes (in red) are the 1992 19. 06.28.1992 4:57 am Landers 7.3 magnitude 7.3 Landers and 1999 magnitude 20. 06.28.1992 8:05 am Big Bear 6.3 21. 01.17.1994 4:30 am Northridge 6.7 7.1 Hector Mine earthquakes in the Mojave 22. 10.16.1999 2:46 am Hector Mine 7.1 23. 12.22.2003 11:15 am San Simeon 6.5

THE RESOURCE MINE: To learn more see the web resources listed on page 32. 5 SOUTHERN CALIFORNIA FAULTS California. Over time, these four faults produce about half of the significant earth- The earthquakes of California are caused by quakes of our region.

care? the movement of huge blocks of the earth’s crust. Southern California straddles the However, this is not the whole picture. Unlike boundary between the Pacific and North Central and Northern California, much of the American plates. These large sections of the plate movement in Southern California is not earth’s crust (the North American plate parallel to the San Andreas fault. Between extends east to Iceland while the Pacific plate the southern end of the San Joaquin Valley

Why should I extends west to Japan) are moving past each and the San Bernardino mountains, in the other. The Pacific plate is moving northwest, so-called “big bend,” the San Andreas fault scraping horizontally past North America runs in a more westerly direction. Don’t be fooled! Don’t “BEACHFRONT PROPERTY at a rate of about 50 millimeters (2 inches) IN ARIZONA” Where the fault bends, plate motion is #2 per year. complex. The Pacific and North American The idea of California falling About two-thirds of this 50 millimeters per MYTH plates push into each other, compressing the into the ocean has had an year occurs on the San Andreas fault and earth’s crust into the mountains of Southern enduring appeal to those some parallel faults — the San Jacinto, California and producing faults and earth- envious of life in the Golden Elsinore, and Imperial faults (see map). These State. Of course, the ocean quakes. While these 300 or so faults are gen- four faults are among the fastest moving, and is not a great hole into which erally much shorter and slower moving than California can fall, but it is therefore most dangerous, in Southern the four faults mentioned previously, over half itself land at a somewhat lower elevation with water above it. The motion of plates will not make California sink NORTH — western California is mov- AMERICAN ing horizontally along the San PLATE Andreas fault and up around the Transverse ranges. PACIFIC PLATE

UL A

S SCIGN A DA E A GPS station R EV D N

N A

A RR

N IE

A S S G N Compression zone ARLOCK FAULT

San Gabriel Mountains SIERRA MADRE FAULT

0 60 MILES LT

0 60 KILOMETERS Los Angeles FA

Basin TO

FAULT Pacific C

JA Ocean N A

ELSINORE

1 San Andreas fault

2 San Jacinto fault

k A schematic block model of Southern California showing the motion of the 3 Elsinore fault Pacific and North American plates, and 4 Imperial fault the big bend of the San Andreas fault where the plates squeeze together.

6 Why should I care?

of the significant earthquakes in Southern Geologic rates California occur on these faults. The rate of plate movement along the San Andreas fault, 33 millimeters (1.3 inches) The greatest concentration of these faults is each year, is about how fast your fingernails in and near the mountains that have formed grow. As a result, Los Angeles City Hall is around the big bend of the San Andreas fault now 2.7 meters (9 feet) closer to San (the San Bernardino, San Gabriel, and Santa Francisco than when it was built in 1924. Ynez mountains). These mountains, like most It would take a mere (geologically speaking) mountains in California, are there because 2 million years for your nails to extend 100 earthquakes are pushing them up. Many of these faults can be seen at the earth’s kilometers (60 miles) from San Bernardino to surface, though some are buried beneath the Palmdale. It took many millions of years of SCIGN station located in Elysian Park near movement on faults (earthquakes) to shape sediments of the Los Angeles basin and the downtown Los Angeles inland valleys. Southern California’s current landscape. Unknown faults

As the Northridge earthquake confirmed, some k SCEC Community Fault Model. This map shows the 3-dimensional structure of major faults beneath faults are not known until they move in large Southern California. Vertical faults such as the San Andreas (yellow band from top left to bottom right) are and damaging earthquakes. What do we do shown as a thin strip. Faults that are at an angle to the surface are shown as wider ribbons of color. The about these unknown faults we can’t see and nearest fault to you might be a few miles beneath your home. Areas that seem to have few faults can still don’t know about yet? Do we still have to wait experience strong shaking from earthquakes on unmapped faults or from large earthquakes on distant faults. until the next earthquake reveals them? Not necessarily. In 2001, scientists of the Southern California Earthquake Center completed the Southern California Integrated GPS Network (SCIGN), an advanced system of 250 Global Positioning System (GPS) receivers. With this network the positions of locations throughout Southern California can be precisely measured. This network is now a part of an even larger system, the Plate Boundary Observatory, which is measuring movement throughout the western United States. By measuring these locations for several years, we can see how different sites are moving relative to each other—for instance, Palos Verdes is moving toward Pasadena at about 4 millimeters (5/32 inch) per year. If movement between two locations is greater than the movement on known faults, then we have a reasonable idea that there may be another fault in the area, perhaps buried by sediment. This can lead to focused research using other methods to identify the unknown fault.

3 2

7 care? Why should I

EARTHQUAKE SHAKING POTENTIAL IN SOUTHERN CALIFORNIA

We could worry about every one of the more than 300 faults described on the previous page. But we do not need to. As described on pages 28 and 29, the ground shaking in an earthquake depends on the magnitude, the distance from the fault, and local soil conditions. So earthquakes on distant faults may not be a threat to you.

However, since there are faults throughout the region, in the long run most areas of Southern California will experience heavy earthquake shaking. Some locations will experience such shaking more frequently because they are closer to more faults or have local soil conditions that amplify earthquake shaking (see pages 28 and 29 for more information). These regions are near major, Unfortunately, scientists do not yet have the active faults and will on average information needed to predict which earth- experience stronger earthquake shaking more frequently. This quakes will happen first, so we must be ready intense shaking can damage for the shaking in our area from any possible even strong, modern buildings. earthquake. To help, scientists have combined the probable shaking from all our known faults to create the large map above. It shows

the relative intensity of ground shaking in INCREASING INTENSITY These regions are distant from California from all anticipated future earth- known, active faults and will quakes. Areas in red and pink are nearer experience lower levels of shaking less frequently. In most major, active faults and on average experience earthquakes, only weaker stronger earthquake shaking more frequently. masonry buildings would be damaged. However, very infre- Although the greatest hazard is in these areas, quent earthquakes could still no region within the state is immune from the cause strong shaking here. potential for earthquake damage.

8 Why should I care?

CALIFORNIA

9 OTHER EARTHQUAKE-RELATED Seismic Hazard Zones (SHZs) identify areas HAZARDS IN SOUTHERN CALIFORNIA that may be prone to liquefaction or landsliding triggered by earthquake shaking. Lique-

care? The previous pages have described where faction is a temporary loss of strength in the earthquakes have happened, the many faults ground that can occur when certain water in Southern California capable of large earth- saturated soils are shaken during a strong quakes, and the expected shaking from future earthquake. When this occurs buildings can earthquakes. In addition to these regional settle, tilt, or shift. Landsliding can occur aspects of the earthquake hazard, there are during an earthquake where shaking reduces Why should I location-specific hazards that can cause addi- the strength of the slope. These hazards can tional damage: surface rupture, liquefaction, usually be reduced or eliminated through and landslides. The California Geological established engineering methods. The law Survey produces maps that identify requires that property being developed within Earthquake Fault Zones and Seismic Hazard these zones be evaluated to determine if a Zones where these hazards may occur. State hazard exists at the site. If so, necessary laws require that every person starting to “put design changes must be made before a permit down roots” by buying a home or real proper- is granted for residential construction. Being ty in California be told if the property is in in an SHZ does not mean that all structures in one of these zones. the zone are in danger. The hazard may not Earthquake Fault Zones (EFZs) recognize the exist on each property or may have been hazard of surface rupture that might occur mitigated. Mapping new SHZs in urban and during an earthquake where an active fault urbanizing areas is ongoing statewide. meets the earth’s surface. Few structures can Current zones, as established by the withstand fault rupture directly under their California Geological Survey, are indexed at foundations. The law requires that within an www.consrv.ca.gov/cgs. EFZ most structures must be set back a safe distance from identified active faults. The Don’t be fooled! Don’t “AND THE EARTH necessary setback is established through geo- OPENED…” #3 logic studies of the site. EFZs are narrow A popular literary device is a strips along the known active surface faults MYTH fault that opens during an wherein these studies are required prior to earthquake to swallow up an development. Being located in an EFZ does annoying character. But unfor- not necessarily mean that a building is on a tunately for principled writers, fault. Most of the important known faults in gaping faults exist only in nov- California have been evaluated and zoned, els. The ground moves across and modifications and additions to these a fault during an earthquake, not away from it. If the fault zones continue as we learn more. could open, there would be no friction. Without friction, there would be no earthquake.

LA County Juvenile Hall, Sylmar, California, damaged by liquefaction during the magnitude 6.6 San Fernando earthquake of February 9, 1971. The broken floor is due to settling of the earth and is not the fault itself. Photo by Jack Meehan, structural engineer.

10 Why should I care?

SANTA BARBARA SAN BERNARDINO VENTURA LOS ANGELES

RIVERSIDE SANTA ANA Area evaluated for Seismic Hazard Zones as of 2003 SAMPLE AREA

SAN DIEGO

1 mile

k Red zones are Earthquake Fault Zones with potential for 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.

Earthquake Fault Zone (EFZ): Seismic Hazard Zone (SHZ) see “sample area” above see “sample area” above

11 What should I do? 12 TO EARTHQUAKESAFETY THE SEVENSTEPS the riskofbeinginjuredorkilled. next largeearthquake.Mostimportantly, wecanreduce follow thesesteps,wemaysavebillionsofdollarsinthe lowed inschools,workplaces,andotherfacilities.Ifweall to followingthestepsathome,theyshouldalsobefol- when structuresandcontentsarenotdamaged.Inaddition after earthquakes.Thestepsmayalsosavealotofmoney can besaferbyknowingwhattodobefore,during,and The sevenstepsdescribedinthissectionshowhowwe that breakorfallonpeoplecausinginjury. better, moreofthelossesinearthquakesarefromobjects collapsing buildings.Again,no!Asbuildingsaredesigned damage andinjuriesfromearthquakescomes take before,during,andafter. Manyalsothinkthatallthe Earthquake damageandlosscanbelimitedbystepsyou is topickupthepiecesaftershakingstops.No! by earthquakesisunavoidable,andthatouronlyoption quakes isnot.Manypeoplethinkthedestructioncaused Earthquakes areinevitable,butthedamagefromearth- start here… workplace forournextearthquake. your home,school,and Follow thesesevenstepstoprepare section. following thesevenstepsdescribedinthis Daretoprepareby Doyourpart. recovery. quake damageandinjuries,tospeed ing, andafterearthquakes,toreduceearth- Alliance allhavespecificrolesbefore,dur- The membersoftheEarthquakeCountry organizations. existing resourcesandtheadviceofmany The recommendationsarebasedonmany business andcommunityleaders,others. emergency managers,governmentofficials, leadingearthquakeprofessionals, includes the EarthquakeCountry Alliance, which These stepsweredevelopedbymembersof What shoud I do?

When safe, continue to follow your disaster-preparedness plan.

After the earthquake, check for injuries and damage.

Protect yourself during earthquake shaking—DROP, COVER AND HOLD ON.

Identify your building’s potential weaknesses and begin to fix them.

Prepare disaster supplies kits.

Create a disaster- preparedness plan.

Identify potential hazards in your home and begin to fix them.

THE RESOURCE MINE: To learn more see the web resources listed on page 32. 13 IDENTIFY POTENTIAL In the kitchen #1 HAZARDS IN YOUR HOME Unsecured cabinet doors fly open during do? AND BEGIN TO FIX THEM. earthquakes, allowing glassware and dishes to crash to the floor. Many types of latches Earthquake safety is more than minimizing are available to prevent this: child-proof damage to buildings. We must also secure the latches, hook and eye latches, or positive contents of our buildings to reduce the risk to catch latches designed for boats. Gas appli- our lives and our pocketbooks. ances should have flexible connectors to

What should I reduce the risk of fire. Secure refrigerators Several people died and thousands were and other major appliances to walls using injured in the Northridge earthquake because earthquake appliance straps. 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- vented in advance through simple actions to secure buildings and contents.

You should secure anything 1) heavy enough to hurt you if it falls on you, or 2) fragile or expensive enough to be a significant loss if it falls. In addition to contents within your living space, also secure items in other areas, such as your garage, to reduce damage to Electronics vehicles or hazardous material spills. Televisions, stereos, computers and microwaves and other electronics are heavy There may be simple actions you can do right and costly to replace. They can be secured now that will protect you if an earthquake with flexible nylon straps and buckles for happens tomorrow. START NOW by moving easy removal and relocation. furniture such as bookcases away from beds, sofas, or other places where people sit or sleep. Move heavy objects to lower shelves. Then begin to look for other items in your home that may be hazardous in an earthquake. Don’t be fooled! Don’t “WE HAVE GOOD BUILD- Some of the actions recommended on this

#4 ING CODES SO WE MUST HAVE GOOD BUILDINGS.” page may take a bit longer to complete, but all are relatively simple. Most hardware stores MYTH The best building codes in the and home centers now carry earthquake safety world do nothing for buildings straps, fasteners, and adhesives. built before a code was enact- ed. While the codes have been updated, the older buildings are still in place. Fixing Additional information, including problems in older buildings — how-to instructions, is available at retrofitting — is the responsi- bility of the building’s owner. www.daretoprepare.org

14 What shoud I do?

Furniture Secure the tops of all top-heavy furniture, such as bookcases and file cabinets, to a wall. Be sure to anchor to the stud, and not just to the drywall. Flexible fasteners such as nylon straps allow tall objects to sway without falling over, reducing the strain on the studs. Loose shelving can also be secured by apply- ing earthquake putty on each corner bracket.

Objects on open shelves and tabletops Water heater

Collectibles, pottery objects, and lamps can Unsecured water heaters often fall become deadly projectiles. Use either hook over, rupturing rigid water and and loop fasteners on the table and object, or gas connections. If your water non-damaging adhesives such as earthquake heater does not have two putty, clear quake gel, or microcrystalline straps around it that are wax to secure breakables in place. Move screwed into the studs or heavy items and breakables to lower shelves. 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 connectors, if not already done.

In the garage or utility room

Hanging objects Items stored in garages and utility rooms can fall, causing injuries, damage, and hazardous Mirrors, framed pictures, and other objects spills or leaks. They can also block access to should be hung from closed hooks so that vehicles and exits. Move flammable or haz- they can’t bounce off the walls. Pictures and ardous materials to lower shelves or the floor. > Move on to#2 mirrors can also be secured at their corners once you have identified with earthquake putty. Only soft art such as potential hazards, have fixed tapestries should be placed over beds or some, and have a plan for sofas. fixing the rest. > > > > > >

The seven steps to earthquake safety

BEFORE: DURING: AFTER:

#5 #6 #7 #1 #2 #3 #4 Drop, cover, Check for When safe, Identify and fix Create Prepare disaster Identify and fix and hold on. injuries and continue to hazards in your a disaster- supplies kits. your building’s (Page 19) damage. follow your home. preparedness (Page 17) weaknesses. (Page 20) disaster plan. plan. (Page 18) (Page 21) (Page 16)

15 do?

Plan NOW to be safe during an earthquake: Plan NOW to communicate and recover after an earthquake: Practice “drop, cover, and hold on.” What should I (See Step 5, page 19) Select a safe place outside of your home to meet Identify safe spots in every room, such as under your family or housemates after the shaking sturdy desks and tables. stops. Learn how to protect yourself no matter where Designate an out-of-area contact person who you are when an earthquake strikes. can be called by everyone in the household to relay information. Plan NOW to respond after an earthquake: Provide all family members with a list of important contact phone numbers. #2 Keep shoes and a working flashlight next to Determine where you might live if your home each bed. cannot be occupied after an earthquake or other CREATE A DISASTER- Teach everyone in your household to use disaster. PREPAREDNESS PLAN. emergency whistles and/or to knock three times Know about the earthquake plan developed by repeatedly if trapped. Rescuers searching your children's school or day care. Keep your Will everyone in your household do the right collapsed buildings will be listening for sounds. children's school emergency release card current. thing during the violent shaking of a major Identify the needs of household members and neighbors with special requirements or situa- Keep copies of essential documents, such as earthquake? Before the next earthquake, get tions, such as use of a wheelchair, walking aids, identification, insurance policies, and financial together with your family or housemates to special diets, or medication. records, in a secure, waterproof container, and plan now what each person will do before, Take a Red Cross first aid and cardiopulmonary keep with your disaster supplies kits. Include a during and after. resuscitation (CPR) training course. Learn who household inventory (a list and photos or video of else in your neighborhood is trained in first aid your belongings). Once the earthquake is over, we will have to and CPR. Know the location of utility shutoffs and keep Have occasional earthquake “drills” to live with the risk of fire, the potential lack of needed tools nearby. Make sure you know how practice your plan. Share your plan with utilities and basic services, and the certainty to turn off the gas, water, and electricity to your people who take care of your children, pets, of aftershocks. By planning now, you will be home. Only turn off the gas if you smell or hear or home. ready. This plan will also be useful for other leaking gas. Get training from your local fire department in emergencies. how to properly use a fire extinguisher. Install smoke alarms and test them monthly. Change the battery once a year, or when the alarm emits a "chirping" sound (low-battery signal). Check with your city or county to see if there is a Move on to Community Emergency Response Team (CERT) in > #3 your area. If not, ask how to start one. once you have your plan, create your disaster supplies kits that you’ll use when you follow your plan after an earthquake. > > > > >

The seven steps to earthquake safety

BEFORE: DURING: AFTER:

#5 #6 #7 #1 #2 #3 #4 Drop, cover, Check for When safe, Identify and Create Prepare disaster Identify and fix and hold on. injuries continue to fix hazards a disaster- supplies kits. your building’s (Page 19) and damage. follow your in your home. preparedness weaknesses. (Page 20) disaster plan. (Page 14) plan. (Page 18) (Page 21)

16 What shoud I do?

PREPARE DISASTER SUPPLIES KITS.

Personal disaster supplies kits

Everyone should have personal disaster supplies kits. Keep them where you spend most of your time, so they can be reached even if your building is badly damaged. The kits will be useful for many emergencies.

Keep one kit in your home, another in your car, and a third kit at work. Backpacks or other small bags are best for your disaster supplies kits so you can take them with you if you evacuate. Include at least the following items:

Medications, prescription list, copies of medical List of emergency out-of-area contact cards, doctor's name and contact information phone numbers Medical consent forms for dependents Snack foods, high in water and calories First aid kit and handbook Working flashlight with extra batteries and Examination gloves (non-latex) light bulbs, or light sticks Dust mask Personal hygiene supplies Spare eyeglasses or contact lenses and Comfort items such as games, crayons, writing cleaning solution materials, teddy bears Bottled water Toiletries and special provisions you need for Whistle (to alert rescuers to your location) yourself and others in your family including Sturdy shoes elderly, disabled, small children, and animals. Emergency cash Copies of personal identification (drivers license, Road maps work ID card, etc.) A special note Household disaster supplies kit about children Electrical, water, transportation, and other vital systems can be disrupted for several days after a large earthquake. Emergency response agencies and hospitals could be overwhelmed and unable If earthquakes scare us because we feel out of to provide you with immediate assistance. Providing first aid and having supplies will save lives, control, think how much more true this must be for will make life more comfortable, and will help you cope after the next earthquake. children, who already must depend on adults for so much of their lives. It is important to spend time In addition to your personal disaster supplies kits, store a household disaster supplies kit in an with children in your care before the next earth- easily accessible location (in a large watertight container that be easily moved), with a three-day quake to explain why earthquakes occur. Involve to one-week supply of the following items: them in developing your disaster plan, prepare disaster supplies kits, and practice “drop, cover, Wrenches to turn off gas and water supplies Charcoal or gas grill for outdoor cooking and Work gloves and protective goggles matches if needed and hold on.” Consider simulating post-earth- Heavy duty plastic bags for waste, and to serve Cooking utensils, including a manual can opener quake conditions by going without electricity or as tarps, rain ponchos, and other uses Pet food and pet restraints tap water. Portable radio with extra batteries Comfortable, warm clothing including extra socks Additional flashlights or light sticks Blankets or sleeping bags, and perhaps even a After the earthquake, remember that children will Drinking water (minimum one gallon per person, tent be under great stress. They may be frightened, per day) Copies of vital documents such as insurance their routine will probably be disrupted, and the Canned and packaged foods policies aftershocks won’t let them forget the experience. Use and replace perishable items like water, food, medications and batteries on a yearly basis. Adults tend to leave their children in order to deal with the many demands of the emergency, but this can be devastating to children. Extra contact and > Move on to #4 support from parents in the early days will pay off

to consider how to reduce damage to your home later. Whenever possible, include them in the and serious injury from building collapse. >> recovery process.

17 do?

What should I #4

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

Buildings are designed to withstand the k This cutaway diagram shows how weak cripple walls can be strengthened by properly attached downward pull of gravity, yet earthquakes plywood sheets. shake a building in all directions — up and down, but most of all, sideways. There are Common building problems several common issues that can limit a building’s ability to withstand this sideways Most houses are not as safe as they could be. Soft first stories. Look for larger openings in shaking. The following presents some common struc- the lower floor, such as a garage door or a tural problems and how to recognize them. hillside house built on stilts. Consult a pro- Additional information, including Once you determine if your building has one fessional to determine if your building is ade- how-to instructions, is available at or more of these problems, prioritize how quately braced. www.daretoprepare.org and when to fix them, and get started. Unreinforced masonry. All masonry (brick Inadequate foundations. Look under your or block walls) should be reinforced. Some house at your foundation. If the foundation is communities have a program for retrofitting For those who rent damaged or built in the “pier and post” style, buildings made of unreinforced masonry. consult a contractor or engineer about replac- If your house has masonry as a structural As a renter, you have less control over the ing it with a continuous perimeter foundation. element consult a structural engineer to find structural integrity of your building, but you Look for bolts in the mudsills. They should be what can be done. Inadequately braced do control which apartment or house you no more than 1.8 meters (6 feet) apart in a chimneys are a more common problem. rent: single story and 1.2 meters (4 feet) apart in a Consult a professional to determine if your • Structures made of unreinforced brick or multistory building. Adding bolts to unse- chimney is safe. block walls can collapse and cause great cured houses is one of the most important loss of life. If you live in a mobile home... • Apartment buildings with "tuck-under" steps toward earthquake safety. This can be parking space openings can also collapse. done by a contractor or by someone skilled at Look under your home. If you only see a • Foundation and cripple wall failures can home maintenance. metal or wood “skirt” on the outside with cause expensive damage but less loss of life. concrete blocks or steel tripods or jacks • Objects attached to the sides of buildings, Unbraced cripple walls. Homes with a crawl such as staircases, balconies, and decora- supporting your home, you need to have an space should have panels of plywood connect- tions, can break off in earthquakes. “engineered tie-down system” or an “earth- ing the studs of the short “cripple” walls (see quake-resistant bracing system” (ERBS) Ask your landlord these questions: figure). You or a contractor can strengthen the installed. An ERBS should have a label on • What retrofitting has been done on this cripple walls relatively inexpensively. building? the bracing that says, “Complies with the • Have the water heaters been strapped to the California Administrative Code, Title 25, wall studs? Chapter 2, Article 7.5.” • Can I secure furniture to the walls?

18 What shoud I do?

PROTECT YOURSELF DURING Driving: Pull over to the side of the road, EARTHQUAKE SHAKING— stop, and set the parking brake. Avoid over- DROP, COVER, AND HOLD ON. passes, bridges, power lines, signs and other hazards. Stay inside the vehicle until the The previous pages have concentrated on shaking is over. If a power line falls on the getting ready for the next earthquake. What car, stay inside until a trained person removes should you do during and after earthquakes? the wire.

During earthquakes, drop to the floor, take If you are… In a stadium or theater: Stay at your seat and cover under a sturdy desk or table, and hold protect your head and neck with your arms. Indoors: Drop, cover, and hold on. If you on to it firmly. Be prepared to move with it Don’t try to leave until the shaking is over. are not near a desk or table, drop to the floor until the shaking stops. Then walk out slowly watching for anything against the interior wall and protect your that could fall in the aftershocks. The area near the exterior walls of a building head and neck with your arms. Avoid exterior is the most dangerous place to be. Windows, walls, windows, hanging objects, mirrors, Near the shore: Drop, cover and hold on until facades and architectural details are often the tall furniture, large appliances, and kitchen the shaking stops. Estimate how long the first parts of the building to collapse. To stay cabinets with heavy objects or glass. Do not shaking lasts. If severe shaking lasts 20 sec- away from this danger zone, stay inside if go outside! onds or more, immediately evacuate to high you are inside and outside if you are outside. ground as a tsunami might have been gener- In bed: If you are in bed, hold on and stay ated by the earthquake. Move inland 3 kilo- there, protecting your head with a pillow. You meters (2 miles) or to land that is at least 30 are less likely to be injured staying where meters (100 feet) above sea level immediate- you are. Broken glass on the floor has caused ly. Don't wait for officials to issue a warning. injury to those who have rolled to the floor or Walk quickly, rather than drive, to avoid traf- tried to get to doorways. fic, debris and other hazards. In a high-rise: Drop, cover, and hold on. Below a dam: Dams can fail during a major Avoid windows and other hazards. Do not earthquake. Catastrophic failure is unlikely, use elevators. Do not be surprised if sprinkler but if you live downstream from a dam, you systems or fire alarms activate. “HEAD FOR THE Don’t be fooled! Don’t should know flood-zone information and DOORWAY.” Outdoors: Move to a clear area if you can have prepared an evacuation plan. #5 An enduring earthquake safely do so; avoid power lines, trees, signs, image of California is a col- MYTH buildings, vehicles, and other hazards. lapsed adobe home with the door frame as the only stand- ing part. From this came our belief that a doorway is the The seven steps to earthquake safety safest place to be during an earthquake. True—if you live BEFORE: DURING: AFTER: in an old, unreinforced adobe house. In modern houses, doorways are no stronger #6 #7 #4 #5 Check for When safe, than any other part of the Identify and fix Drop, cover, injuries and continue to house. You are safer under a your building’s and hold on. damage. follow your weaknesses. (Page 20) disaster plan. table. (Page 21)

19 AFTER THE EARTHQUAKE, #6 CHECK FOR INJURIES AND DAMAGE do?

First take care of your own situation. Check for damage Remember your emergency plans. • FIRE. If possible, put out small fires in Aftershocks may cause additional damage or your home or neighborhood immediately. items to fall, so get to a safe location. Take Call for help, but don’t wait for the fire your disaster supplies kit. department. What should I If you are trapped by falling items or a • GAS LEAKS. Shut off the main gas valve collapse, protect your mouth, nose, and eyes only if you suspect a leak because of from dust. If you are bleeding, put pressure on broken pipes or the odor or sound of the wound and elevate the injured part. Signal leaking natural gas. Don’t turn it back on for help with your emergency whistle, a cell yourself — wait for the gas company to phone, or knock loudly on solid pieces of the check for leaks. The phone book has building, three times every few minutes. detailed information on this topic. Rescue personnel will be listening for such • DAMAGED ELECTRICAL WIRING. Shut off sounds. power at the main breaker switch if there is any damage to your house wiring. Leave Once you are safe, help others and check for the power off until the damage is repaired. damage. Protect yourself by wearing sturdy • BROKEN LIGHTS AND APPLIANCES. shoes and work gloves, to avoid injury from Unplug these as they could start fires when broken glass and debris. Also wear a dust electricity is restored. mask and eye protection. • DOWNED POWER LINES. If you see downed power lines, consider them energized and Check for injuries stay well away from them. Keep others away • Check your first aid kit or the front pages from them. Never touch downed power “EVERYONE WILL PANIC Don’t be fooled! Don’t of your telephone book for detailed lines or any objects in contact with them. DURING THE BIG ONE!” instructions on first aid measures. • FALLEN ITEMS. Beware of items tumbling #6 A common belief is that peo- • If a person is bleeding, put direct pressure off shelves when you open closet and ple always panic and run on the wound. Use clean gauze or cloth, if cupboard doors. MYTH around madly during and after available. • SPILLS. Use extreme caution. Clean up any earthquakes, creating more • If a person is not breathing, administer spilled medicines, drugs, or other non-toxic danger for themselves and others. Actually, research rescue breathing. substances. Potentially harmful materials shows that people usually • If a person has no pulse, begin CPR such as bleach, lye, garden chemicals, and take protective actions and (cardiopulmonary resuscitation). gasoline or other petroleum products should help others both during and • Do not move seriously injured persons be isolated or covered with an absorbent after the shaking. Most people unless they are in immediate danger of such as dirt or cat litter. When in doubt, don’t get too shaken up about being shaken up! further injury. leave your home. • Cover injured persons with blankets or • DAMAGED MASONRY. Stay away from additional clothing to keep them warm. chimneys and walls made of brick or block. • Get medical help for serious injuries. They may be weakened and could topple The seven steps • Carefully check children or others needing during aftershocks. Don’t use a fireplace to earthquake safety special assistance. with a damaged chimney. It could start a AFTER: fire or let poisonous gases into your home. #6 #7 Check for injuries When safe, and damage. continue to follow your disaster plan.

20 What shoud I do?

WHEN SAFE, CONTINUE Food and water #7 TO FOLLOW YOUR • If power is off, plan meals to use up refrig- DISASTER-PREPAREDNESS erated and frozen foods first. If you keep PLAN. the door closed, food in your freezer may be good for a couple of days. • Listen to your radio for safety advisories. Once you have met your and your family's • If your water is off or unsafe, you can immediate needs after an earthquake, contin- drink from water heaters, melted ice cubes, ue to follow the plan you prepared in advance or canned vegetables. Avoid drinking water If you cannot stay in (see Step 2, page 16). Aftershocks will continue from swimming pools or spas. your home… to happen for several weeks after major • Do not eat or drink anything from open earthquakes. Some may be large enough to If your home is structurally unsafe or threat- containers that are near shattered glass. cause additional damage. Always be ready to ened by a fire or other hazard, you need to evacuate. However, shelters may be over- drop, cover, and hold on. The first weeks after the earthquake… crowded and initially lack basic services, so Your recovery period can take several weeks do not leave home just because utilities are This is a time of transition. Although after- out of service or your home and its contents to months or longer. Take the actions listed shocks may continue, you will now work have suffered moderate damage. below to be safe and to minimize the long- toward getting your life, your home and term effects of the earthquake on your life. If you evacuate, tell a neighbor and your out- family, and your routines back in order. of-area contact where you are going. As soon The first days after the earthquake… Emotional care and recovery are just as as possible, set up an alternative mailing important as healing physical injuries and address with the post office. Take the follow- Use the information you put together in your rebuilding a home. Make sure your home is ing, if possible, when you evacuate: disaster plan and the supplies you organized safe to occupy and not in danger of collapse Personal disaster supplies kits in your disaster kits. Until you are sure there in aftershocks. If you were able to remain in Medications and eyewear are no gas leaks, do not use open flames Supply of water, food, and snacks your home or return to it after a few days, (lighters, matches, candles, or grills) or oper- Blanket/pillow/air mattress or sleeping pad you will have a variety of tasks to accom- Change of clothing and a jacket ate any electrical or mechanical device that plish: Towel and washcloth can create a spark (light switches, generators, Diapers, food, and other supplies for infants motor vehicles, etc.). Never use the following • If your gas was turned off, you will need to A few family pictures or other comfort items indoors: camp stoves, gas lanterns or heaters, arrange for the gas company to turn it back Personal identification and copies of gas or charcoal grills, or gas generators. on. household and health insurance information. These can release deadly carbon monoxide or • If the electricity went off and then came Do not take to a shelter: be a fire hazard in aftershocks. back on, check your appliances and elec- • Pets (Service animals for people with tronic equipment for damage. disabilities are allowed; take food for them. Be in communication • If water lines broke, look for water damage. Have a plan for your pets in advance.) • Turn on your portable or car radio for • Locate and/or replace critical documents • Large quantities of unnecessary clothing or other personal items information and safety advisories. that may have been misplaced, damaged, • Valuables that might be lost, stolen, or take • Place all phones back on their cradles. or destroyed. up needed space • Call your out-of-area contact, tell them • Contact your insurance agent or company your status, then stay off the phone. right away to begin your claims process. Once a Presidential Declaration has been issued, FEMA may activate the Individuals Emergency responders need to use the • Contact the Federal Emergency and Households Program. This program phone lines for life-saving communica- Management Agency (FEMA) to find out includes: tions. about financial assistance • Home-repair cash grants; the maximum • Check on the condition of your neighbors. (www.fema.gov/about/process/). Federal grant available (as of 2005) is $26,200 • Housing Assistance in the form of reim- bursement for short-term lodging at a hotel • Rental assistance for as long as 18 months in the form of cash payment Once you have recovered from the earthquake, go back to Step 1 and do • If no other housing is available, FEMA may the things you did not do before, or do them more thoroughly. Learn from what provide mobile homes or other temporary housing happened during the earthquake so you will be safer next time.

21 What should I do? losses andassistinourrecovery. help ustakeactionsnowtoreducepotential ing wherefuturedamageislikelytooccurcan tents, andbusinessinterruption.Understand- bridge damage,destructionofbuildingcon- since 1971. These lossesincludebuilding and duced over$60billioninlossesCalifornia (see graphofdisastercosts). They havepro- Earthquakes areCalifornia’s costliestdisasters CALIFORNIA OF EARTHQUAKESIN REDUCING THECOSTS 22 from severaldisasterssince1971,compared using2003dollars. Earthquakes areCalifornia’s costliestdisasters. Thischartshowslosses California’s CostliestDisasters Disaster Billions (2003 Dollars) 10 20 30 40 50 60

1987 Whittier Narrows Earthquake

1993 So. California

Fires seismic retrofit. is uptoyoustrengthenyourbuildingbya apply tonewconstruction,soinmostcasesit their property. Betterbuilding codesonly sibility fortheirsafetyandtheprotectionof to respond,andindividualsmusttakerespon- gency managersmustbeequippedandready quakes mustbestrengthenedorrebuilt,emer- needed. Olderbuildingsatriskfromearth- in futureearthquakesmuchmoreworkis recent earthquakes.However, toreducelosses reduced thedeaths,injuriesanddamagein gency managementorganizations have strengthened highwaystructures,andemer- California’s enhancedbuildingcodes, much higher. buildings, fatalitiesanddamagewouldbe more denselypopulatedareawitholder Northridge earthquakeweretooccurina earthquake thesizeofmagnitude6.7 construction, andmanyotherfactors.Ifan structures areinthearea,qualityof on thepatternofintenseshaking,howmany Damage causedbyanearthquakedepends

1991 Oakland Fires

1971 San Fernando Earthquake

2003 So. California Fires

1995 Statewide Flooding

1989 Loma Prieta Earthquake

1994 Northridge Earthquake • • • • factors toconsider: home andbelongings.Herearesome damage earthquakesmaycausetoyour able toreduceyourrisk. This canlimitthe prepare andprotectyourself,youmaybe questions aboutyourrisksandtakestepsto in earthquakecountry. Ifyouasktheright You areatriskforalossifyouownproperty earthquake risk Understanding yourpotential costs istobuyearthquakeinsurance. ings. Oneoptionformanagingthese potential and youwillneedtorepairorreplace belong- home willstillhavesomelevelofdamage, the stepsinthishandbook,itislikelyyour and personalbelongings.Evenifyoufollow earthquake strikesanddamagesyourhome dream canbecomeanightmarewhenan becoming ahomeowner. Inseconds,your secure yourpieceofthe American Dreamby biggest singleasset. You haveworkedhardto If youownyourhomeitisprobably Earthquake insuranceinCalifornia Losses Risk–Identifying Hazards andEstimating guidance suggestedin potential lossestotheirhomecanfollowthe Individuals interestedinestimatingthe • property. are availableandhowtheymightbenefityour foundation? Learnwhatretrofittingprograms a cripplewall,orisyourhomerestingonslab your home.Doyouhavearaisedfoundationwith 14) Consider theageandtypeofconstruction page 1, Step (See Are yourbelongingsproperlysecured? of anearthquake. what risksthesoiltypemightbringinevent Know whattypeofsoilyourhomeisbuilton,and liquefaction orlandslides. earthquake faultsorareasthatcanhave property inrelationshiptoidentifiedandactive Consider thegeographiclocationofyour how wouldyourecoverandrebuild? devastating earthquakedestroysyourproperty, equity doyouhaveinyourproperty?Ifa property, includingyourbelongings.Howmuch Consider theinvestmentyouhaveinyour available fromFEMA. (See Step 4, page 18) page 4, Step (See (See page 29) page (See Understanding Your (See page 10) page (See

What shoud I do? k Annualized earthquake loss ratios at the county level To understand potential losses from future disasters, the Federal Emergency Management Agency (FEMA) developed a software program called HAZUS. This program combines information about expected shaking, building types and locations, population, and other factors to calculate the severity of damage that an earthquake may cause and resulting costs. This allows officials to estimate the impacts of an earthquake without having to wait for it to occur. This map shows expected losses each year for counties in the United States, averaged over many years. Los Angeles County has the highest expected loss of any county in the country, at Earthquake insurance in California is typical- Many companies issue California Earthquake over $1 billion each year on ly not part of your homeowners insurance Authority (CEA) insurance policies, which average. In addition, the policy; it is generally a separate policy you are designed to rebuild your home if it suffers Southern California region con- can purchase when buying homeowners significant damage from an earthquake. tains almost half the Nation’s insurance. All insurance companies that sell $4.4 billion in projected annualized loss. residential property insurance in California You may purchase a CEA policy only are required by law to offer earthquake insur- through the CEA’s participating insurers. ance to homeowners when the policy is first A complete list is on the CEA web site at sold and then every two years thereafter. www.earthquakeauthority.com, which has an online premium calculator. The cost of the earthquake policy you are offered is based on a number of factors, Contact your homeowners insurance including your home’s location, age, con- company or agent to help you evaluate your struction type, and value. It is up to each earthquake risk factors and then consider homeowner to consider their individual risk whether earthquake insurance is a good factors and then weigh the cost of earthquake choice for you. coverage against the benefits that coverage may offer after a devastating earthquake.

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

What should I . er 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 rupture surface area of your fingertip and thumb, earthquakes happen over an area of the fault, called the hypocenter 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 fault plane called the hypocenter, a point usually deep down on the fault. The epicenter is the point on the surface directly above the hypocenter.

fault line The rupture keeps spreading until something epicenter stops it (exactly how this happens is a hot research topic in seismology). hypocenter Aftershocks Part of living with earthquakes is living with aftershocks. Earthquakes come in clusters. In any earthquake cluster, the largest one is called the mainshock; anything before it is a foreshock, and anything after it is an aftershock.

24 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 Surface features that have been broken and followed by a larger earthquake. Then the 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. For days the risk is almost gone. example, a streambed that crosses the San Andreas fault near Los Angeles is now offset 83 Sometimes, the chance that an event is a fore- meters (91 yards) from its original course. The shock seems higher than average — usually sediments in the abandoned streambed are because of its proximity to a major fault. The about 2,500 years old. If we assume movement Number of earthquakes in the region of the mainshock Governor’s Office of Emergency Services will Year on the San Andreas has cut off that streambed then issue an advisory based on scientists’ rec- within the last 2,500 years, then the average ommendations. These are the only officially slip rate on the fault is 33 millimeters (1.3 Aftershocks are earthquakes that usually recognized short-term “predictions.” inches) per year. This does not mean the fault occur near the mainshock. The stress on the What is a fault? slips 33 millimeters each year. Rather, it stores mainshock’s fault changes during the main- up 33 millimeters of slip each year to be shock and most of the aftershocks occur on Earthquakes occur on faults. A fault is a thin released in infrequent earthquakes. The last the same fault. Sometimes the change in zone of crushed rock separating blocks of the earthquake offset the streambed another 5 stress is great enough to trigger aftershocks on earth’s crust. When an earthquake occurs on meters (16 feet). If we assume that all earth- nearby faults as well. one of these faults, the rock on one side of the fault slips with respect to the other. Faults can quakes have 5 meters (5000 millimeters) of slip, An earthquake large enough to cause damage be centimeters to thousands of kilometers we will have earthquakes on average every 150 will probably produce several felt aftershocks long. The fault surface can be vertical, hori- years: 5000 millimeters divided by 33 millime- within the first hour. The rate of aftershocks zontal, or at some angle to the surface of the ters per year equals 150 years. This does not dies off quickly. The day after the mainshock earth. Faults can extend deep into the earth mean the earthquakes will be exactly 150 years has about half the aftershocks of the first day. and may or may not extend up to the earth’s apart. While the San Andreas fault has aver- Ten days after the mainshock there are only surface. aged 150 years between events, earthquakes a tenth the number of aftershocks. An earth- have occurred as few as 45 years and as many quake will be called an aftershock as long as How do we know a fault exists? as 300 years apart. the rate of earthquakes is higher than it was • Past fault movement has brought together before the mainshock. For big earthquakes, rocks that used to be farther apart; Carrizo Plain National Monument along this might go on for decades. the San Andreas fault • Earthquakes on the fault have left surface Bigger earthquakes have more and larger evidence, such as surface ruptures or fault aftershocks. The bigger the mainshock, the scarps (cliffs made by earthquakes); bigger the largest aftershock, on average, though there are many more small aftershocks • Earthquakes recorded by seismographic than large ones. Also, just as smaller earth- networks are mapped and indicate the quakes can continue to occur for many years location of a fault. after a mainshock, there is still a chance for a large aftershock long after an earthquake. Some faults have not shown these signs and we will not know they are there until they produce a large earthquake. Several damaging earthquakes in California have occurred on faults that were previously unknown.

THE RESOURCE MINE: To learn more see the web resources listed on page 32. 25 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 the We define the epicenter of an earthquake with adjoining piece of ground, causing it to the latitude and longitude of a point, but the vibrate, and thus the energy travels out from 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, vibrates and this vibration is recorded. and even the epicenter can only be determined Don’t be fooled! Don’t “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 of city streets is like giving the location of MYTH earthquakes are more com- the S-wave (a shear wave). The S-wave is your city by the address of City Hall. mon in certain kinds of slower but larger than the P-wave and does weather. In fact, no correla- most of the damage. Scientists have used How big was the earthquake? tion with weather has been found. Earthquakes begin knowledge of the differences between these Why do scientists have problems coming up many kilometers below the and other seismic waves to learn a great deal with a simple answer to this simple question? region affected by surface about the interior of the earth. weather. People tend to Many people have felt this frustration after notice earthquakes that fit the Knowing how fast seismic waves travel earthquakes, as seismologists often seem to pattern and forget the ones through the earth, seismologists can calculate contradict one another. In fact, earthquakes that don’t. Also, every region are very complex. Measuring their size is of the world has a story about the time when the earthquake occurred and earthquake weather, but the its location by comparing the times when something like trying to determine the “size” type of weather is whatever shaking was recorded at several stations. This of an abstract modern sculpture with only one they had for their most memo- process used to take almost an hour when use of a tape measure. Which dimension do rable earthquake. done manually. you measure?

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 seconds the ground in one earthquake is 10 times the maximum acceleration in another earthquake,

k These seismograms show how the ground then the first earthquake is said to be one moved at four seismic stations during an unit of magnitude larger than the second. The earthquake. The time when ground starts shaking is the arrival of the P-wave. The ground starts Richter Scale, as it became known, is not a shaking sooner and shakes more at sites nearer device, but the range of numbers used to the earthquake. compare earthquakes.

26 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 9.2 March 27, 1964 Alaska 1,000 420 mean there will be 1,000 times more shaking at your home. A bigger earthquake will last 7.9 November 3, 2002 Denali, AK 300 90 longer and release its energy over a much 7.9 January 9, 1857 Fort Tejon, CA 360 130 larger area. 7.8 April 18, 1906 San Francisco, CA 400 110 7.2 - 7.8 February 7, 1812 New Madrid, MO 40–100 13–30 7.3 June 28, 1992 Landers, CA 70 24 Seismologists have since developed a new 7.3 August 17, 1959 Hebgen Lake , MT 44 12 measurement of earthquake size, called 7.0 October 17, 1989 Loma Prieta, CA 40 7 moment magnitude. Moment is a physical 7.0 October 28, 1983 Borah Peak, ID 34 9 quantity more closely related to the total 6.8 February 28, 2001 Nisqually, WA 20 6 energy released in the earthquake than Richter 6.7 January 17, 1994 Northridge, CA 14 7 magnitude. It can be estimated by geologists 6.4 March 10, 1933 Long Beach, CA 15 5 examining the geometry of a fault in the field 5.9 October 1, 1987 Whittier Narrows, CA 6 3 or by seismologists analyzing a seismogram. 5.8 June 28, 1991 Sierra Madre, CA 5 2 Because the units of moment are very large, it 5.2 September 3, 2001 Yountville (near Napa), CA 4 2 has been converted to the more familiar range of magnitude values for communication to For comparison, the largest earthquake ever recorded was a moment magnitude 9.5 in Chile on May 18, 1960. 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 magnitude of that earthquake can be calculated with confidence.

k Shown are the 100 stations of the Advanced National Seismic System's (ANSS) backbone network. When completed the ANSS will include 1,000 regional stations in areas of active seismicity and 6,000 strong motion stations in 26 urban areas at risk to damaging earthquakes. These stations will build upon the existing networks of seismographs already existing in high-seismic areas such as Southern California, and improve the accuracy of locating and measuring earthquakes throughout the country.

27 What should I know? M6.7 Northridge 28 M6.8 Nisqually Earthquake Earthquake 1994 2001 and localsoilconditions. by threemainfactors:magnitude,distance, What youfeelinanearthquakeiscontrolled duration (howlongthestrongshakinglasts). frequencies justlikesoundwaves),andthe quency (seismicwavesvibrateatdifferent speed ofthegroundischanging),fre- is moving),acceleration(howquicklythe described bythevelocity(howfastground with onenumber. Aspects ofthemotionare jerky orrolling—andisnotdescribable very complex—hardorgentle,longshort, sure oftheshakingyoufeel. What youfeelis produced byanearthquakeandisnotamea- Magnitude isameasurementoftheenergy EARTHQUAKE SHAKING at least50kilometers(30miles)away fromthefault. Northridge earthquake.Thereforeevery housewas much deeperthanthefaultthatmoved inthe reason isthatthesectionoffaultmovedwas scale, theresultingdamagewasfarless.One than theNorthridgeearthquakeonmagnitude though theNisquallyearthquakewasslightlylarger affects thelevelofshakingexperienced.Even esting exampleofhowdistancefromanearthquake (M6.7) earthquakesshownaboveprovideaninter- k The 2001Nisqually(M6.8)and1994Northridge away andyouwillfeelarolling motion. away, thehigherfrequencieswillhavedied the earthquakeandfeel“jolted.” Farther will experiencealltheshakingproducedby noises). Ifyouarenearanearthquake, farther awaythanyoucanhigh-pitched (just asyoucanhearlow-pitchednoisesfrom with distancethandohigh-frequencywaves Low-frequency wavesdiminishlessrapidly shaking islessintensefartherfromthefault. they travelthroughtheground,soearthquake Earthquake wavesdiminishinintensityas Distance very strong. from thepartoffaultnearestyouwillbe 10–15 secondsofshakingthatoriginates ters (250miles)away. Inmost cases,onlythe the energy willbetravelingfrom400 kilome- quake frightensyou,rememberthatsomeof minutes. Iftheideaofatwo-minuteearth- 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 off shaking,solongerfaultsproduce ing. Everypointcrossedbytherupturefront fault, producingwavesallthetimeitismov- from theretherupturefronttravelsalong An earthquakebeginsatahypocenter, and time. over alarger areaandforalongerperiodof Bigger earthquakesalsoreleasetheirenergy from abigearthquakethansmallone. Typically youwillfeelmoreintenseshaking Magnitude What should I know?

14 more shaking

20 miles

less shaking

softer

101 harder 5 405

101 134 210

110 101 surface 10

1 10 4 m iles 110 15 dee KILOMETERS p

015 710 605 N 1 MILES 5 135 010 405 Amplification Relative Shaking in Future Earthquakes In these images of the Los Angeles Basin, the lowest layer S C E C shows the depth of sedimentary basins, and the middle layer 5 shows the softness of near-surface rocks and sediments. The top layer is the total amplification expected in future earth- Earthquake Ground-Motion Amplification in Southern California quakes because of these features.

The amount of damage to a building does not Local soil conditions The same factors also apply to areas covered depend solely on how hard it is shaken. In Soils can greatly amplify the shaking in an by thick sediment — such as the Los Angeles general, smaller buildings such as houses are earthquake. Passing from rock to soil, seismic basin in Southern California where sediments damaged more by higher frequencies, so waves slow down but get bigger. Hence a can be as much as 10 kilometers (6 miles) usually houses must be relatively close to the soft, loose soil may shake more intensely than thick. Shaking from an earthquake in the hypocenter to be severely damaged. Larger hard rock at the same distance from the same region can be 5 or more times greater at a site structures such as high-rises and bridges are earthquake. An extreme example for this type in the basin than the level of shaking in the damaged more by lower frequencies and will of amplification was in the Marina district of nearby mountains. be more noticeably affected by the largest San Francisco during the 1989 Loma Prieta P.S. earthquakes, even at considerable distances. earthquake. That earthquake was 100 kilome- The shaking dies off with distance more ters (60 miles) from San Francisco, and most Several other factors can affect shaking. quickly in the western United States than in of the Bay Area escaped serious damage. Earthquake waves do not travel evenly in all the older, more rigid crust of the eastern However, some sites in the Bay Area on land- directions from the rupture surface; the United States. fill or soft soils experienced significant shak- orientation of the fault and the direction of ing. This amplified shaking was one of the movement can change the characteristics of reasons for the the collapse of the elevated the waves in different directions. This is Nimitz freeway. Ground motion at those sites called the radiation pattern. When the earth- was more that 10 times stronger than at neigh- quake rupture moves along the fault, it boring sites on rock. focuses energy in the direction it is moving so that a location in that direction will receive more shaking than a site at the same distance from the fault but in the opposite direction. This is called directivity.

29 What should I know? 30 Last Week Last Day Last Hour earthquake). 5:30 am,January17,1994(onehouraftertheNorthridge Recent EarthquakesMap AFTER EARTHQUAKES INFORMATION AVAILABLE valuable information. quake, andhowyoucanalsoprovide from variousorganizations afteranearth- describes informationthatwillbeavailable understand whattoexpectnext. This page happened canreduceourfearandhelpus ing andconfusing.Knowingwhatjust Experiencing anearthquakecanbefrighten- intensity isdesignatedbyRomannumerals. ing tocatastrophic intensity thatrangefromimperceptibleshak- shaking accordingtoincreasinglevelsof much damagewascaused.Bothsystemsmap they wereshakenandobservationsofhow uses inputfrompeopleabouthowstrongly sure thisshaking,while“Did You FeelIt?” center. ShakeMapusesinstrumentstomea- usually decreasingwithdistancefromtheepi- value butwillhavemanyvaluesforintensity, singleearthquakewillhaveonemagnitude A duced bytheearthquakeatacertainlocation. intensity describesthelevelofshakingpro- the totalenergy releasedbytheearthquake, Intensity Scale. While magnitudedescribes intensities similartotheModifiedMercalli of shakingexperiencedintermsarange shown ontheoppositepageexpresslevel The ShakeMapand“Did You FeelIt?”maps Mapping theintensityofshaking more commonlyused(see less likelyasmomentmagnitudebecomes mometers andtechniques. This has become earthquake, becauseofdifferences inseis- times reportdifferent magnitudesfor thesame of anearthquake. These networkswillsome- far willcalculatethemagnitudeandlocation throughout theworld,networksbothnearand Because wavesfromlarge earthquakestravel Center atwww visit theSouthernCaliforniaEarthquakeData For recentSouthernCaliforniaearthquakes, in theirregion. generated mapsandlistsofrecentearthquakes (ANSS) havewebsiteswithautomatically the Advanced NationalSeismicSystem tion withinafewminutes.Localnetworksof calculate anearthquake’s magnitudeandloca- Modern seismicnetworkscanautomatically Recent earthquakemaps .data.scec.or destruction. The levelof page 27 g ). What should I know?

ShakeMap Instrumental Intensity Map (ShakeMap) 1994 Northridge earthquake Modern seismic networks, with digital instruments and high-speed communications, have enabled seismic data to be used in new and innovative ways. A product of these new networks is ShakeMap, which shows the distribution of ground shaking in a region. This information is critical for emergency management. ShakeMaps are automatically generated and distributed on the Internet for most felt earthquakes (to view maps for Southern California earthquakes, visit . www.cisn.org/shakemap). This information may save lives and speed recovery efforts.

ShakeMap was first developed for Southern California as part of the TriNet Project, a joint effort by the U.S. Geological Survey (USGS), California Institute of Technology PERCEIVED SHAKING Not felt Weak Light Moderate Strong Very strong Severe Violent Extreme (Caltech), and the California Geological POTENTIAL DAMAGE none none none Very light Light Moderate Moderate/Heavy Heavy Very Heavy Survey (CGS). 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 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 INSTRUMENTAL INTENSITY I II-III IV V VI VII VIII IX X+

Community Internet Intensity Map (“Did You Feel It?”) “Did You Feel It?” community-made 1994 Northridge earthquake earthquake shaking maps

93534

93532 Not long ago, the first thing that most people did after feeling an earthquake was to turn on PALMDALE 93551 their radio for information. Now many people

93552

91384

CASTAIC 91390 are getting this information via the Internet, 93543

93550

93510 and sharing their experience of the earthquake

91354

91351 91350 91387 91355 online. “Did You Feel It?” is a web site devel- 93015

93060 91381 91321 oped by the USGS (and regional seismic net- 91342

93021 works) that allows people to share information 93066 93063 91344 93004 93065 91311 91340 91326 91042

91345 91040 NORTHRIDGE91331 about the effects of an earthquake. Visitors to 91330 91324 91343 91325 91214 93010 91352 91402 91304 91011

91360 91020 93012 91306 91605 91307 91405 91504 91501 91335 91406 91303 91208 91001 the site enter their ZIP code and answer a list 91362 91606 91377 91207 91411 91401 91505 91502 91367 91506 91601 91201 91607 91202 91104 91024 91316 PASADENA91103 91016 91206 91107 93033 91364 91356 91436 91602 91203 91403 91423 91361 91101 91010 91320 91604 91608 91105 91106 of questions such as “Did the earthquake wake 91301 91204 91205 90041 91006 91702 90068 91007 90027 91302 91108 91775 93042 90039 90042 90065 91030 90077 90046 91780 90290 90210 90028 91706 91722 90069 91801 91776 90038 90029 90049 9 you up?” and “Did objects fall off shelves?” 90272 90026 90031 90032 90004 91803 91732 90048LOS ANGELES 90095 90036 91790 91770 90265 90024 90211 90020 90012 90212 90010 90057 917 90067 90005 90017 91754 90035 90033 91755 90019 90006 91733 90025 90013 90063 90263 90015 90402 90064 90403 90034 91744 90016 90007 These responses are converted to intensities 90404 90022 90232 90023 90401 90640 90405 90008 90011 90037 91745 90066 90601 SANTA MONICA 90291 90230 90056 90043 90270 90660

91748 90292 90255 90606 90302 90001 for each ZIP code and within minutes a map is 90201 90602

90301 90240 90293 90045 90044 90002 90605 90280 90603 90241 90631 90303 90670 90604 90262 90242 90245 created on the Internet that is comparable to 90250 90650 92835 90249 90638 90723 90247 90266 90260 90706 92833 9283 90248 90220 90621 90278 92832 90504 90703 90254 90805 ShakeMaps produced from seismic data. The 90746

90712 90623 90713 90620 92801 90503 90715 90502 90501 92805 90277 90807 90745 90808 92804 90630 92802 90505 map is updated frequently as people submit 90806 90680 90710 90815 km 90717 90720 92841 92840 90804 90744 90813 90274 90814 92844 92843 90802 90803 90275 90740 92683 92703 reports. Such “Community Internet Intensity 0 10 20 30 92655 90731 90732 92647 92649 92704 90742 5048 responses in 627 ZIP areas. Max intensity: IX 92708 Maps” contribute greatly in quickly assessing

92648 92626 the scope of an earthquake emergency, espe- INTENSITY I II-III IV V VI VII VIII IX X+ cially in areas lacking seismic instruments. To SHAKING Not felt Weak Light Moderate Strong Very strong Severe Violent Extreme

DAMAGE none none none Very light Light Moderate Moderate/Heavy Heavy Very Heavy report your experience of an earthquake, visit earthquake.usgs.gov/eqcenter/dyfi.php.

31 THE RESOURCE MINE

Answers for many of your questions, additional resources for the sections below, and online versions of the Southern California and San Francisco Bay Region editions of this handbook in multiple languages can be found at: www.earthquakecountry.info

Why should I care? (Page 4) Historic Earthquakes in Southern California clickable map: www.data.scec.org/clickmap.html care? Recent Earthquakes in Southern California: www.data.scec.org/recenteqs.html Southern California clickable fault map: www.data.scec.org/faults/faultmap.html California Geological Survey – Seismic Shaking Hazard Maps: www.consrv.ca.gov/CGS/rghm/psha/pga.htm Landslide and Liquefaction Maps for Southern California: gmw.consrv.ca.gov/shmp Why should I

What should I do? (Page 12) Earthquake Country Alliance: www.daretoprepare.org do? American Red Cross: www.redcross.org California Earthquake Authority: www.earthquakeauthority.com California Seismic Safety Commission: www.seismic.ca.gov Emergency Survival Program (ESP): www.espfocus.org California Office of Emergency Services: www.oes.ca.gov Federal Emergency Management Agency: www.fema.gov What should I “Step 1” in greater detail: www.quakeinfo.org

What should I know? (Page 24) United States Geological Survey Earthquake Hazards Program: earthquake.usgs.gov California Geological Survey: www.consrv.ca.gov/cgs know? Southern California Earthquake Center: www.scec.org Southern California Earthquake Data Center: www.data.scec.org Recent Earthquakes in Southern California: www.data.scec.org/recenteqs.html Southern California ShakeMaps: www.cisn.org/shakemap Did You Feel It? - report it!: earthquake.usgs.gov/eqcenter/dyfi.php What should I

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