Putting down roots in country

SPRING 2005

Your Handbook for Living in Southern Your

Developed by the Southern California Earthquake Center United States Geological Survey National Science Foundation California Earthquake Authority Federal Emergency Management Agency Introduction “Every day is earthquake season in California” in season earthquake is day “Every headquartered attheUniversityofSouthernCalifornia. Science FoundationandtheUnitedStatesGeologicalSurvey, SCEC isaresearchconsortiumsupportedbytheNational (SCEC). Reproductionbypermissiononly. Copyright 2005,SouthernCaliforniaEarthquakeCenter Goltz; Emergency Services: Sylvester, DougBausch,Jeffrey Lusk; 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 Vikki Appel,EgillHauksson; American RedCross: Turner; Charles Real; Shaw; (p. 14,16,18,19). (p. 17,21);JereSmith(cover, p.2,3,32);andRobertZimmerman 29); StephanieLangley(p.4,6,10,14,19,20, 26); Punchstock Connor (p.14–15);DaleGlasgow24);Min Jae Hong(p.16,19, Illustrators: Elizabeth Burrill Design: Jeff Primes;and 2 California GeologicalSurvey: KFWB: California EarthquakeAuthority: Denton DesignAssociates:MargiS.Denton, Lucile M.Jones,USGSandMarkBenthien,SCEC Mark BenthienandRobertdeGroot,SCEC(second The suggestionsandillustrationsincludedinthis Elizabeth Burrill(p.12–13);DanielClark18); Todd California SeismicSafetyCommission: Jack Popejoy; SCEC (USC): Members oftheEarthquakeCountryAlliance Peggy Brutsche,RockyLopes; Greg Renick,DeborahSteffen,James FEMA: Ilene Cooper, ThomasHenyey, John Harvard: Trevco: Hassaan Sughayer, Dennis Jerry Treiman, ChrisWills, Dean Reese,BrianLowe, Andreas Plesch,John California Officeof Nanci Kinkaid; is aservice USGS: Caltech: 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 it takeswhentheearthshakes,wearereadyforearthquakes In SouthernCalifornia, and alsowhatweshould quakes inSouthernCalifornia,whatwecan This handbookprovidesinformationaboutwhyweshould what todoafterearthquakes. to theirfoundations.We arepracticing“drop,cover, andholdon”learning and disastersupplieskits.We aremakingsureourhomesproperlysecured them frombeingdamagedorcausinginjury. We arecreatingdisasterplans On apersonallevel,wearesecuringbelongingsandwaterheaterstokeep structing buildingsthatwillnotcollapseandbridgessway, notbreak. and wearelearninghowtoreducethelossesfromearthquakes.We arecon- the freeways.We havelearnedtosurfthewavesandnavigatefreeways, areasSouthernCalifornianwavesatthebeachandtrafficon can comeatanytime,soearthquakes. What should I do? 22 21 20 19 18 17 16 14 12 to EarthquakeSafety The SevenStepsontheRoad Reducing thecostsofearthquakesinCalifornia #7:Whensafe,followmydisasterplan. STEP and injuriesneedingimmediateattention. #6:Aftertheshakingstops,checkfordamage STEP Drop, cover, andholdon. #5:Duringearthquakesandaftershocks: STEP and begintofixthem. #4:Identifymybuilding’s potential weaknesses STEP #3:Createmydisastersupplieskits. STEP #2:Createmydisasterplan. STEP begin tofixthem. #1:Identifypotentialhazardsinmyhomeand STEP The sevenstepsontheroadtoearthquakesafety every day day every know about earthquakebasics.Whenweknowwhat is “earthquakeseason.”Justlikesunnydays do to besafeandreducedamage,

What should I know? care 32 32 The ResourceMine 30 28 26 25 24 Earthquake Basics Books andotherprintedpublications Web resources Information availableafterearthquakes Earthquake shaking Locating andmeasuringearthquakes Faults Earthquakes every day. every about earth- 3 Introduction SOUTHERN CALIFORNIA IS EARTHQUAKE COUNTRY We know that the 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 earth- quakes will shake the ground and cause other hazards such as liquefaction and landslides. Finally, the damage earthquakes can cause is discussed with ways of reducing your potential losses. 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 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: Web resources, books, and other printed publications (see 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 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 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

1

T

L

U

A

F

S SCIGN A DA E A GPS station R EV

D N

N A

A RR

N IE

A S S GA N Compression zone RLOCK FAULT

San Gabriel Mountains SIERRA MADRE FAULT 0 60 MILES

0 60 KILOMETERS Los Angeles LT Basin U FA Pacific TO CIN FAULT

JA

Ocean N

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S

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. 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

1

4

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 condi- tions that amplify earthquake shaking.

Unfortunately, scientists do not yet have the These regions are near major, information needed to predict which earth- active faults and will on average quakes will happen first, so we must be ready experience stronger earthquake shaking more frequently. This for the shaking in our area from any possible intense shaking can damage earthquake. To help, scientists have combined even strong, modern buildings. the probable shaking from all our known faults to create the large map above. It shows the relative intensity of ground shaking in

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

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 landslid- ing 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 building site. EFZs are A popular literary device is a narrow strips along the known active surface MYTH fault that opens during an faults wherein these studies are required prior earthquake to swallow up an to 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? #7 #6 #5 #4 #3 #2 #1 12 TO EARTHQUAKESAFETY THE SEVENSTEPSONROAD we canreducetheriskofbeinginjuredorkilled. of dollarsinthenextlargeearthquake.Mostimportantly, facilities. Ifweallfollowthesesteps,maysavebillions should alsobefollowedinschools,workplaces,andother damaged. Inadditiontofollowingthestepsathome,they save alotofmoneywhenstructuresandcontentsarenot before, during,andafterearthquakes.Thestepsmayalso can besaferinthenextearthquakebyknowingwhattodo The sevenstepsdescribedinthissectionshowhowwe that breakorfallonpeoplecausinginjury. better, moreofthelossesinearthquakesarefromobjects collapsing buildings.Again,no!Asbuildingsaredesigned damage andinjuriesfromearthquakescomes take before,during,andafter. Manyalsothinkthatallthe Earthquake damageandlosscanbelimitedbystepsyou to pickupthepiecesaftershakingstops.No! by earthquakesisunavoidable,andthatouronlyoption quakes isnot.Manypeoplethinkthedestructioncaused Earthquakes areinevitable,butthedamagefromearth- When safe,followmydisasterplan. immediate attention. After theshakingstops,checkfor damage andinjuriesneeding AFTER: drop, cover, andholdon. During earthquakesandaftershocks: DURING: and begintofixthem. Identify mybuilding’s potentialweaknesses Create mydisastersupplieskits. Create mydisasterplan. Identify potentialhazardsinmyhomeandbegintofixthem. BEFORE: SEVEN STEPS: (Page 20) (Page (Page 18) (Page (Page 16) (Page (Page 19) (Page (Page 17) (Page (Page 21) (Page (Page 14) (Page What shoud I do?

THE RESOURCE MINE: Web resources, books, and other printed publications (see page 32) 13 IDENTIFY POTENTIAL #1 HAZARDS IN MY HOME do? AND BEGIN TO FIX THEM. In the kitchen

Earthquake safety is more than minimizing Unsecured cabinet doors fly open during damage to buildings. We must also secure the earthquakes, allowing glassware and china contents of our buildings to reduce the risk to to crash to the floor. Many types of latches our lives and our pocketbooks. are available to prevent this — child-proof latches, hook and eye latches, or positive What should I Four people died in the Northridge earthquake catch latches designed for boats. Gas appli- because of unsecured building contents such ances should have flexible connectors to as toppling bookcases. Many billions of dol- reduce the risk of fire. lars were lost due to this type of damage.

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 liv- ing space, also secure items in other areas, such as your garage, to reduce damage to vehicles or hazardous material spills.

There may be simple actions you can do right now that will protect you if an earthquake happens tomorrow. Look around and see if Electronics there is a bookcase that can be easily moved TVs, stereos, computers, microwaves, and to a safer location now or a heavy object on a other electronics are heavy and costly to high shelf that can be moved lower or secured replace. They can be secured with flexible in place now. Test your smoke alarm battery. nylon straps and buckles for easy relocation.

Some of the actions recommended on this page may take a bit longer to complete, but all are relatively simple. Most hardware stores and home centers now carry earthquake safety

Don’t be fooled! Don’t straps, fasteners, and adhesives. “WE HAVE GOOD BUILD-

#4 ING CODES SO WE MUST HAVE GOOD BUILDINGS.” MYTH The best building codes in the world do nothing for buildings built before a code was enact- ed. While the codes have been updated, the older build- ings are still in place. Fixing problems in older buildings — retrofitting — is the responsi- bility of the building’s owner.

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. Store heavy items and breakables on lower shelves. Loose shelving can also be secured by applying earthquake putty on each corner bracket. Tabletop objects

Collectibles, china, pottery objects, and lamps can become deadly projectiles. Use either hook and loop fasteners on the table and object, or non-damaging adhesives such as earthquake putty, clear quake gel, or microcrystalline wax to secure breakables in place.

Water heater You will be able to see straps and screws if your water heater is braced. Make sure the screws are firmly anchored to studs or masonry with appropriate screws. This illustration shows one method of bracing Hanging objects a water heater. Bracing kits are > Move on to#2 Mirrors, framed pictures, and other objects available that can once you have identified potential should be hung from closed hooks so that make this process hazards, have fixed some, and have they can’t bounce off the walls. Pictures and simple. a plan for fixing the rest. > > > > > mirrors can also be secured at their corners with earthquake putty. Only soft art such as tapestries should be placed over beds or sofas.

I can follow the seven steps on the road to earthquake safety

BEFORE: DURING: AFTER:

#5 #6 #7 #1 #2 #3 #4 Drop, cover, Check for When safe, Identify Create my Create my Identify my building’s and hold on. damage and follow my potential disaster plan. disaster potential weak- (Page 19) injuries needing disaster plan. hazards in my (Page 16) supplies kits. nesses and begin attention. (Page 21) home and begin (Page 17) to fix them. (Page 20) to fix them. (Page 18)

15 do?

What I should learn and practice: What I should prepare:

I Practice “drop, cover, and hold on.” I Identify safe spots in every room, such as under

What should I (See Step 5, page 19) sturdy desks and tables. I Teach children and adults to use an emergency I Keep shoes and a working flashlight next to whistle and/or to knock 3 times if trapped. each bed. Rescuers searching collapsed buildings will be I Locate a safe place to meet after the shaking listening for sounds. stops, outside of your home. I Know the location of utility shutoffs and keep I Establish an out-of-area contact person who can needed tools nearby. Know how to turn off the be called by everyone in the household to relay gas, water, and electricity to your home. The information. #2 preparedness section of your phone book has I Determine where you might live if your home information on this topic. cannot be occupied after an earthquake or other CREATE MY DISASTER PLAN. I Know how to operate the emergency latch on disaster (ask friends or relatives). your garage door opener in case of power out- I Keep copies of essential documents, such as Will everyone in your household do the right age or damage to your garage door. insurance policies and financial records, in a thing during the violent shaking of a major I Get training from your local fire department in secure location such as with your disaster how to properly use a fire extinguisher. supplies kits. Include a household inventory (a earthquake? Before the next earthquake, get I Install smoke alarms and test them monthly. list and photos or video of your belongings). together with your family or housemates to Change the battery once a year, or when the I Provide children with an emergency cell phone plan now what you will do before, during and alarm emits a "chirping" sound which is a low- or list of phone numbers with instructions to con- after. battery signal. firm their location and condition after an earth- I Locate your nearest fire and police stations and quake. Program the phone with important con- Once the earthquake is over, we will have to emergency medical facility. tact numbers. I I Keep your children’s school emergency release live with the risk of fire, the potential lack of Take a Red Cross first aid and cardiopulmonary resuscitation (CPR) training course. card current. utilities and basic services, and the certainty I Learn who in your neighborhood is trained in I Address needs of household members and of aftershocks. By planning now, you will be first aid. neighbors with special requirements or situa- ready. This plan will also be useful for other I Check with your fire department to see if there is tions, such as use of a wheelchair, walking aids, emergencies. a Community Emergency Response Team (CERT) special diets, or medication. in your area. If not, ask them how to start one. I Ask school staff about the earthquake plan developed by your children’s school or day care. I Ask your babysitters, house sitters, and a neigh- bors about their disaster plans, and share your plan and essential information with them. I Have occasional earthquake “drills” to practice your plan. > Move on to #3

once you have your plan, create your disaster supplies kits that you’ll use when you follow your plan after an earthquake. > > > > >

I can follow the seven steps on the road to earthquake safety

BEFORE: DURING: AFTER:

#5 #6 #7 #1 #2 #3 #4 Drop, cover, Check for When safe, Identify Create my Create my Identify my building’s and hold on. damage and follow my hazards in my disaster plan. disaster potential weak- (Page 19) injuries needing disaster plan. home and begin supplies kits. nesses and begin attention. (Page 21) to fix them. to fix them. (Page 20) (Page 14) (Page 18)

16 What shoud I do?

#3

CREATE MY DISASTER SUPPLIES KITS.

My 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:

I Medications and medical consent forms I List of emergency out-of-area contact for dependents phone numbers I First aid kit and handbook I Snack foods, high in water and calories I Examination gloves (non-latex) I Working flashlight with extra batteries and I Dust mask light bulbs I Spare eyeglasses or contact lenses and I Personal hygiene supplies cleaning solution I Comfort items such as games, crayons, writing I Bottled water materials, teddy bears I Whistle (to alert rescuers to your location) I Toiletries and special provisions you need for I Sturdy shoes yourself and others in your family including I Emergency cash elderly, disabled, small children, and animals. I Road maps

My household disaster supplies kit A special note Electrical, water, transportation, and other vital systems can be disrupted for several days after a about children large earthquake. Emergency response agencies and hospitals could be overwhelmed and unable to provide you with immediate assistance. Knowing first aid and having supplies will save lives, If earthquakes scare us because we feel out of will make life more comfortable, and will help you cope after the next earthquake. control, think how much more true this must be for children, who already must depend on adults for In addition to your personal disaster supplies kits, store a household disaster supplies kit in an so much of their lives. It is important to spend time easily accessible location (in a large watertight container that be easily moved), with a 3-day to with children in your care before the next earth- 1-week supply of the following items: quake to explain why earthquakes occur. Involve them in developing your disaster plan, prepare I Wrenches to turn off gas and water supplies I Charcoal or gas grill for outdoor cooking and I Work gloves and protective goggles matches if needed disaster supplies kits, and practice “drop, cover, I Heavy duty plastic bags for waste, and to serve I Cooking utensils, including a manual can opener and hold on.” Consider simulating post-earth- as tarps, rain ponchos, and other uses I Pet food and pet restraints quake conditions by going without electricity or I Portable radio with extra batteries I Comfortable, warm clothing including extra socks tap water. I Drinking water (minimum one gallon per person, I Copies of vital documents such as insurance per day) policies After the earthquake, remember that children will I Canned and packaged foods be under great stress. They may be frightened, Use and replace perishable items like water, food, medications and batteries on a yearly basis. their routine will probably be disrupted, and the aftershocks won’t let them forget the experience. Adults tend to leave their children in order to deal with the many demands of the emergency, but this > Move on to #4 can be devastating to children. Extra contact and to consider how to reduce damage to your home support from parents in the early days will pay off and serious injury from building collapse. >> later. Whenever possible, include them in the recovery process.

17 do?

What should I #4

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

Buildings are built to withstand the down- k This cutaway diagram shows how weak cripple walls can be strengthened by properly attached ward pull of gravity, yet earthquakes shake a plywood sheets. building in all directions — up and down, but most of all, sideways. There are several com- Common building problems mon issues that can limit a building’s ability to withstand this sideways shaking. 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 con- tural problems and how to recognize them. necting the studs of the short “cripple” walls Once you determine if your building has one (see figure). You or a contractor can strength- or more of these problems, prioritize how and en the cripple walls relatively inexpensively. when to fix them, and get started. (If you are Soft first stories. Look for larger openings in a renter see box.) For help, refer to the the lower floor, such as a garage door or a For those who rent sources on web sites listed on the back cover hillside house built on stilts. Consult a pro- in the Resource Mine or consult with a pro- fessional to determine if your building is ade- As a renter, you have less control over the fessional contractor or engineer. structural integrity of your building, but you quately braced. do control which building you rent. Inadequate foundations. Look under your Remember these points as you look for rental Unreinforced masonry. All masonry (brick house at your foundation. If the foundation is housing. buildings) should be reinforced. Some com- damaged or built in the “pier and post” style, • Apartment buildings can have many of the munities have a program for retrofitting consult a contractor or engineer about replac- same structural issues as houses. buildings made of unreinforced masonry. If • Structures made of unreinforced masonry ing it with a continuous perimeter foundation. your house has masonry as a structural ele- (such as brick) and with soft first stories Look for bolts in the mudsills. They should be ment consult a structural engineer to find (such as parking space openings) have no more than 1.8 meters (6 feet) apart in a what can be done. Inadequately braced chim- caused great loss of life in earthquakes. single story and 1.2 meters (4 feet) apart in a • Foundation and cripple wall failures have led neys are a more common problem. Consult a multistory building. Adding bolts to unse- to expensive damage but less loss of life. professional to determine if your chimney is • Objects attached to the sides of buildings, cured houses is one of the most important safe. such as staircases and balconies, have often steps toward earthquake safety. This can be broken off in earthquakes, injuring those done by a contractor or by someone moder- below. ately adept at home maintenance.

Ask your landlord these questions: • What retrofitting has been done on this building? • Have the water heaters been strapped to the wall studs? • Can I secure furniture to the walls?

18 What shoud I do?

DURING EARTHQUAKES In bed: If you are in bed, hold on and stay #5 AND AFTERSHOCKS: there, protecting your head with a pillow. You DROP, COVER, AND HOLD ON. are less likely to be injured staying where you are. Broken glass on the floor has caused The previous pages have concentrated on injury to those who have rolled to the floor or getting ready for the next earthquake. What tried to get to doorways. should you do during and after earthquakes? In a high-rise: Drop, cover, and hold on. During earthquakes, drop to the floor, take Avoid windows and other hazards. Do not cover under a sturdy desk or table, and hold use elevators. Do not be surprised if sprinkler on to it firmly. Be prepared to move with it systems or fire alarms activate. until the shaking stops. Outdoors: Move to a clear area if you can The area near the exterior walls of a building safely do so; avoid power lines, trees, signs, is the most dangerous place to be. Windows, buildings, vehicles, and other hazards. facades and architectural details are often the first parts of the building to collapse. To stay Driving: Pull over to the side of the road, away from this danger zone, stay inside if stop, and set the parking brake. Avoid over- you are inside and outside if you are outside. passes, bridges, power lines, signs and other hazards. Stay inside the vehicle until the shaking is over. If a power line falls on the car, stay inside until a trained person removes the wire.

In a stadium or theater: Stay at your seat and protect your head and neck with your arms. Don’t try to leave until the shaking is over. Then walk out slowly watching for anything “HEAD FOR THE Don’t be fooled! Don’t that could fall in the aftershocks. DOORWAY.”

#5 Near the beach: Drop, cover and hold on An enduring earthquake until the shaking stops. Estimate how long image of California is a col- MYTH lapsed adobe home with the If you are… the shaking lasts. If severe shaking lasts 20 door frame as the only stand- seconds or more, immediately evacuate to ing part. From this came our Indoors: Drop, cover, and hold on. If you high ground as a tsunami might have been belief that a doorway is the are not near a desk or table, drop to the floor generated by the earthquake. Move inland 3 safest place to be during an earthquake. True—if you live against the interior wall and protect your kilometers (2 miles) or to land that is at least in an old, unreinforced adobe head and neck with your arms. Avoid exterior 30 meters (100 feet) above sea level immedi- house. In modern houses, walls, windows, hanging objects, mirrors, ately. Don't wait for officials to issue a warn- doorways are no stronger tall furniture, large appliances, and kitchen ing. Walk quickly, rather than drive, to avoid than any other part of the house. You are safer under a cabinets with heavy objects or glass. Do not traffic, debris and other hazards. table. go outside!

I can follow the seven steps on the road to earthquake safety

BEFORE: DURING: AFTER:

#6 #7 #4 #5 Check for When safe, Identify my building’s Drop, cover, damage and follow my potential weak- and hold on. injuries needing disaster plan. nesses and begin to attention. (Page 21) fix them. (Page 20)

19 #6 do?

AFTER THE SHAKING STOPS, Check for damage CHECK FOR DAMAGE • FIRE. If possible, put out small fires in AND INJURIES NEEDING your home or neighborhood immediately. IMMEDIATE ATTENTION. Call for help, but don’t wait for the fire What should I department. First take care of your own situation. • GAS LEAKS. Shut off the main gas valve Remember your emergency plans. only if you suspect a leak because of Aftershocks may cause additional damage or broken pipes or the odor or sound of items to fall, so get to a safe location. leaking natural gas. Don’t turn it back on If you are trapped by falling items or a yourself — wait for the gas company to collapse, protect your mouth, nose, and eyes check for leaks. The phone book has from dust. If you are bleeding, put pressure detailed information on this topic. on the wound and elevate the injured part. • DAMAGED ELECTRICAL WIRING. Shut off power at the main breaker switch if there is If you cannot get out, signal for help with any damage to your house wiring. Leave your emergency whistle, a cell phone, or the power off until the damage is repaired. knock loudly on solid pieces of the building, • DOWNED UTILITY LINES. If you see downed 3 times every few minutes. Rescue personnel power lines, consider them energized and will be listening for such sounds. stay well away from them. Keep others away from them. Never touch downed If you can move, look for another way out power lines or any objects in contact and go to your household meeting place. Take with them. your disaster supplies kit. “EVERYONE WILL PANIC • FALLEN ITEMS. Beware of items tumbling Don’t be fooled! Don’t DURING THE BIG ONE!” Protect yourself by wearing sturdy shoes to off shelves when you open closet and #6 cupboard doors. A common belief is that peo- avoid injury from broken glass and debris. ple always panic and run • SPILLS. Use extreme caution. Clean up any

MYTH Also wear work gloves, a dust mask, and eye around madly during and after protection. Help others, if possible. spilled medicines, drugs, or other non-toxic earthquakes, creating more substances. Potentially harmful materials danger for themselves and Check for injuries such as bleach, lye, garden chemicals, and others. Actually, research gasoline or other petroleum products should shows that people usually • Check your first aid kit or the front pages take protective actions and be isolated or covered with an absorbent of your telephone book for detailed help others both during and such as dirt or cat litter. When in doubt, instructions on first aid measures. after the shaking. Most people leave your home. don’t get too shaken up about • If a person is bleeding, put direct pressure • DAMAGED MASONRY. Stay away from being shaken up! on the wound. Use clean gauze or cloth, if brick chimneys and brick walls. They may available. be weakened and could topple during after- • If a person is not breathing, administer shocks. Don’t use a fireplace with a dam- rescue breathing. I can follow the seven steps on the road aged chimney. It could start a fire or let to earthquake safety • Do not move seriously injured persons poisonous gases into your home. unless they are in immediate danger of AFTER: further injury. If your home is seriously damaged and you • Cover injured persons with blankets or must leave, take your disaster supplies kits additional clothing to keep them warm. #6 #7 with you. Tell your neighbor where you are Check for damage When safe, • Get medical help for serious injuries. and injuries follow my going (relative, hotel, American Red Cross needing disaster plan. • Carefully check children or others needing attention. shelter, etc.). special assistance.

20 What shoud I do?

#7

WHEN SAFE, Long-term recovery FOLLOW MY DISASTER PLAN. Your recovery period can take several weeks Aftershocks will continue to happen for sev- to months or longer. Contact your insurance eral days or weeks after major earthquakes. agent or company right away to begin your Once you have recovered from Always be ready to drop, cover, and hold on. claims process. For most disasters, resources the earthquake, go back to will also be available from the Federal Step 1 and do the things you First one to three days after the earthquake Emergency Management Agency (FEMA), did not do before, or do them Use the information you put together in your state, and local emergency response agencies. disaster plan and the supplies you organized Residents of Presidentially declared disaster more thoroughly. Learn from in your disaster supplies kits. Until you are areas whose homes, businesses or personal what happened during the sure there are no gas leaks, do not use match- property sustained damage as a result of the earthquake so you will be safer earthquake can begin the application process es, lighters, kitchen or camp stoves, barbe- next time. cues, or fuel burning appliances. They may by calling 800-621-FEMA (3362). Those create sparks that could ignite leaking gas with speech or hearing impairments should and cause an explosion and fire. Never use call TTY: 800-462-7585. camp stoves or barbecues indoors. Homeowners and renters whose primary residences are not livable may be eligible for Be in communication funds to pay for temporary housing, repairs • Turn on your portable or car radio for to make the home livable and other serious, information and safety advisories. disaster-caused needs including uncovered • Place all phones back on their cradles. medical, dental or transportation expenses. • Call your out-of-area contact, tell them Depending on your level of damage it may your status, then stay off the phone. be a long time before you are fully recovered Emergency responders need to use the from a large earthquake. Even if your home phone lines for life-saving communications. was not damaged, you may be eligible for • Check on your neighbors. certain forms of disaster aid. It is important • If you cannot live at your home, set up an to know, however, that most govenment alternative mailing address with the post disaster aid to individuals is in the form of a office. loan that must be repaid.

Check your food and water supplies • If power is off, plan meals to use up refrigerated and frozen foods first. If you keep the door closed, food in your freezer may be good for a couple of days. • If your water is off, you can drink from water heaters, melted ice cubes, or canned vegetables. Avoid drinking water from swimming pools or spas. • Listen to your radio for safety advisories. • Do not eat or drink anything from open containers near shattered glass.

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. Betterbuildingcodes only 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 stepsinnextsection,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?

WA ME MT ND OR MN VT NH ID SD WI MA NY MI RI WY CT PA IA NJ NV NE OH DE DC

IN MD

CA IL WV MD CO k UT KS VA Annualized earthquake loss MO KY ratios at the county level NC To understand potential losses TN from future disasters, the Federal OK AZ Emergency Management Agency NM AR SC (FEMA) developed a software GA MS AL program called HAZUS. This program combines information TX about expected shaking, building LA Hawaii FL types and locations, population, and other factors to calculate the severity of damage that an AEL [$M] earthquake may cause and Over 5.0 resulting costs. This allows 1.0 to 5.0 officials to estimate the impacts 0.5 to 1.0 of an earthquake without having 0.1 to 0.5 to wait for it to occur. This map Less than 0.1 shows expected losses each Alaska 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 annual- ized 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 18 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 side- ways 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, releas- ing 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 fore- shock, 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 90 Sometimes, the chance that an event is a fore- meters (98 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 35 millimeters (1 3/8 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 35 millimeters each year. Rather, it stores mainshock’s fault changes during the main- up 35 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 4.5 stress is great enough to trigger aftershocks on earth’s crust. When an earthquake occurs on meters (15 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 4.5 meters (4500 millimeters) of An earthquake large enough to cause damage be centimeters to thousands of kilometers slip, we will have earthquakes on average will probably produce several felt aftershocks long. The fault surface can be vertical, hori- every 130 years: 4500 millimeters divided by within the first hour. The rate of aftershocks zontal, or at some angle to the surface of the 35 millimeters per year equals 130 years. This dies off quickly. The day after the mainshock earth. Faults can extend deep into the earth does not mean the earthquakes will be exactly has about half the aftershocks of the first day. and may or may not extend up to the earth’s 130 years apart. Where the San Andreas fault Ten days after the mainshock there are only surface. has averaged 130 years between events, a tenth the number of aftershocks. An earth- earthquakes have occurred 45 years and 300 quake will be called an aftershock as long as How do we know a fault exists? 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: Web resources, books, and other printed publications (see 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. We

What should I the ground vibrate. That vibration pushes the define the epicenter of an earthquake with the adjoining piece of ground, causing it to 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 !” #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 ground moved 10 times seconds faster in one earthquake than another, then the first earthquake was said to be one unit of

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

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 7.8 January 9, 1857 Fort Tejon, CA 360 130 larger area. 7.7 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 Lake Hebgen, 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 mag- nitude 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 region- al 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 son isthatthesectionoffaultmovedwas scale, theresultingdamagewasfarless.Onerea- 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 wavesdieoff lessrapidly less intensefartherfromthefault. through theearth,soearthquakeshakingis Earthquake wavesdieoff astheytravel 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

5

softer

101 harder 5 405

101 134 210

110 101 surface 10

1 10 4 miles dee KILOMETERS 110 15 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 shows the depth of sedimentary basins, and the middle layer S C E C 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 information. quake, andhowyoucanalsoprovidevaluable from variousorganizations afteranearth- describes informationthatwillbeavailable us understandwhattoexpectnext. This page just happenedcanreduceourfearandhelp ing andconfusingexperience.Knowingwhat Experiencing anearthquakecanbeafrighten- 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 butwillhavemanyvaluesforinten-sity, 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 pages 26and27 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 . earthquake.usgs.gov /shakemap). This infor- mation 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 PERCEIVED SHAKING Not felt Weak Light Moderate Strong Very strong Severe Violent Extreme (USGS), California Institute of Technology POTENTIAL DAMAGE none none none Very light Light Moderate Moderate/Heavy Heavy Very Heavy (Caltech), and the California Geological 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 Survey (CGS). 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

93 91354

91351

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

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

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

91345 91040 NORTHRIDGE91331 about the effects of an earthquake. Visitors to 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 the site enter their ZIP code and answer a list 91606 91377 91207 91367 91411 91401 91505 91502 91506 91201 91601 91202 91104 91024 91316 91607 PASADENA91103 91016 91206 91107 93033 91364 91356 91602 91203 91436 91423 91361 91403 91101 91010 91320 91604 91608 91105 91106 91301 91204 91205 90041 91006 of questions such as “Did the earthquake wake 91702 90068 91007 90027 91302 91108

90039 90042 91775 93042 90065 91030 90077 90046 90290 90210 91780 90028 91706 91722 90069 90029 91801 91776 90049 90038 9 you up?” and “Did objects fall off shelves?” 90272 90026 90031 90032 90004 90048 91803 90095 LOS90036 ANGELES 91732 90020 91790 90265 90024 90211 90012 91770 90212 90010 90057 917 90067 90005 90017 90035 90033 91754 90019 90006 91755 90025 90013 90063 91733 90263 90015 90402 90064 90403 90034 90016 90007 91744 These responses are converted to intensities 90404 90022 90232 90023 90401 90640 90405 90008 90011 90037 90601 90066 91745 SANTA MONICA 90291 90230 90056 90043 90270 90660

90292 90255 90606 90302 90001 91748 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 created on the Internet that is comparable to 90245 90250 90650 90249 90638 92835 90723 90247 90266 90260 90706

90248 90220 92833 9283 90278 90621 90504 90703 92832 90254 90805 ShakeMaps produced from seismic data. The 90746

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

90505 92802 map is updated frequently as people submit 90806 90680 90710 90815 km 90717 90720 92841 90804 92840 90744 90813 90274 90814 92844 92843 90802 90803 90275 90740 reports. Such “Community Internet Intensity 92683 92703 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 pasadena.wr.usgs.gov/shake.

31 THE RESOURCE MINE

Answers for many of your questions, additional resources for the sections below, and the online version of this document 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) American Red Cross: www.redcross.org do? California Earthquake Authority: www.earthquakeauthority.com California Seismic Safety Commission Homeowner's Guide to Earthquake Safety and Commercial Property Owner's Guide to Earthquake Safety: www.seismic.ca.gov/sscpub.htm Emergency Survival Program (ESP): www.cert-la.com/ESP.htm California Office of Emergency Services: www.oes.ca.gov

What should I Federal Emergency Management Agency: www.fema.gov

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.earthquake.usgs.gov/shakemap Did You Feel It? - report it!: pasadena.wr.usgs.gov/shake What should I

Books and other printed publications

Earthquakes by Bruce A. Bolt Furious Earth: The Science and Nature of (ISBN: 0716756188) Earthquakes, Volcanoes, and Tsunamis by Ellen J. Prager (ISBN: 0071351612) Earthshaking Science: What We Know (and Don’t Know) about Earthquakes Geology Underfoot in Southern California by Susan Elizabeth Hough (ISBN: 0691050104) by Robert P. Sharp (ISBN: 0878422897)

Finding Fault in California: Peace of Mind in Earthquake Country An Earthquake Tourist‘s Guide by Peter I. Yanev (ISBN: 0877017719) by Susan Elizabeth Hough (ISBN: 0878424954) www.findingfault.com Living with Earthquakes in California: A Survivor’s Guide by Robert S. Yeats (ISBN: 0870714937)

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