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Home , San Andreas Fault, San Francisco Bay Area

Outlook for the Bay 2014–2043

122°30’ 122° HHU U N T 1 IN M G 72% sing information from

A C 3

A R probability of one or more

C 2 EE recent , E A E U MMA M ≥ 6.7 earthquakes A K 32 improved mapping of

RRO F BERRYESSA from 2014 to 2043 in the O A D U active faults, and a new G LT GREEN Region E R model for estimating 38°30’ S

C 6 VALLEY

R VALLEY earthquake probabilities, E E 8% K F the 2014 Working Group A UULT on Earthquake LT 8 Probabilities updated 16% 22% CONCORD the 30-year earthquake Santa 4 5 Rosa forecast for California. Napa They concluded that there FAULT 9 is a 72 percent probability 13 (or likelihood) of at Faults Point 33% 11 least one earthquake of HAYWARD 12 38° 1 Wight Way Reyes 10 magnitude 6.7 or greater 7 Mill 2 Collayami striking somewhere in the 3 Mysterious Ridge Valley 14 4 Bennett Valley San Francisco Bay San Francisco Bay region Oakland 15 GREENVILLE FAULT 5 West Napa San before 2043. Earthquakes 6 Trout Creek Francisco S FAULT 16 this large are capable 7 A N C of causing widespread A A FAULT 8 Gordon Valley N L D A 18 damage; therefore, 9 Midland S R V a E E n A R communities in the region 10 Franklin F 17 S A

ranc F Fremont S 19 11 Southampton A U F should take simple steps L 30 A i T 12 Los Medanos-Roe Island sco Half Moon U L to help reduce injuries, 13 Pittsburg-Kirby Hills Bay T Bay damage, and disruption, 14 Clayton San Jose 21 37°30’ 20 15 Mt. Diablo North Re as well as accelerate g 16 Mt. Diablo South ion recovery from these 17 Pilarcitos 6% 31 22 earthquakes. 18 Las Positas 26 19 Orestimba 20 Monte Vista-Shannon 25 26% 21 Silver Creek Santa Building damaged in 2014 South 22 Ortigalita North Cruz 23 Napa earthquake. Photograph by 23 Ortigalita South Erol Kalkan, U.S. Geological Survey. 24 Sargent PACIFIC 24 25 Zayante-Vergeles Monterey 28 26 San Joaquin OCEAN Bay 27 Reliz PAICINES FAULT 37° 28 Quien Sabe Salinas 29 27 29 -Tularcitos FAULT 30 Mission Monterey 31 Butano 0 10 20 MILES 32 Dunnigan Hills 0 10 20 KILOMETERS

EXPLANATION Map of known active faults in the San Francisco Bay region. The 72 percent probability Major plate boundary faults of a magnitude 6.7 or greater earthquake includes the well-known major plate-boundary faults, lesser-known faults, and unknown faults. The percentage shown within each 3 Lesser-known smaller faults colored circle is the probability that a magnitude 6.7 or greater earthquake will occur Urban areas somewhere on that fault system by the year 2043. The probability that a magnitude 6.7 or greater earthquake will involve one of the lesser-known faults is 13 percent.

U.S. Department of the Interior Fact Sheet 2016–3020 U.S. Geological Survey Revised August 2016 (ver. 1.1) San Francisco Bay Region Earthquake Timeline

1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

7.8 6.9 6.8 6.4 6.5 6.4 72% 6.3 6.3 6.3 6.2 6.1 6.2 6.1 Probability 6.1 6.1 6.1 6.1 6.1 of at least one 5.9 6.0 6.0 magnitude 6.7 5.9 5.9 5.9 5.9 or greater quake 5.9 5.9 5.9 2014–2043 5.9 5.8 5.9 5.8 5.8 5.8 5.8 5.8 5.8 Increasing earthquake magnitude 5.6 5.7 5.7 5.7 5.7 5.6 5.6 5.6 5.5 5.6 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5

1850–1966 earthquakes from Bakun, W.H., 1999, Seismic Activity of the San Francisco Bay Region: Bulletin Seismological Society of America, v. 89, p. 764–784 and 1967–2014 earthquakes from the Seismic Network.

Earthquake Likelihood of at least one earthquake greater than a given magnitude 5.5–5.9 6.0–6.4 6.5–6.9 >7.0 magnitude in the San Francisco Bay region between 2014 and 2043. Timeline of magnitude 5.5 and greater earthquakes in the Magnitude 30-year likelihood of at least one earthquake San Francisco Bay region 1850–2014. In the 50 years prior to (M) in the San Francisco Bay region 1906, there were 13 earthquakes with a magnitude between M ≥ 6.0 98 percent 6 and 7, but only 6 earthquakes of similar magnitude in M ≥ 6.7 72 percent the 110 years since 1906. The rate of large earthquakes is expected to increase from this low level as tectonic plate M ≥ 7.0 51 percent movements continue to increase the stress on the faults in M ≥ 7.5 20 percent the region.

Earthquake Preparedness Helps earthquake and a clear reminder of the Other major plate boundary faults in the seismic vulnerability of the region. The San Francisco Bay region include the Early Sunday morning on August 24, staff and clients of Becoming Independent Hayward, Rodgers Creek, Calaveras, 2014, the residents of Napa, California, showed that understanding and preparing Maacama, San Gregorio, Concord, were jolted awake by a strong, magnitude for these events can improve how we live Green Valley, and Greenville Faults. 6.0 earthquake. Within 30 minutes, the with future earthquakes. staff of Becoming Independent, a non- How Do Scientists Calculate profit organization that helps adults with Why Does the San Francisco Bay intellectual disabilities lead independent Earthquake Probability? Region Have Earthquakes? lives, called the people they serve in the Scientists rely upon a variety of affected area. The staff quickly visited The same geologic process that is techniques to help understand the rate and all of the clients that needed help with responsible for the San Francisco Bay magnitude of past earthquakes in order cleanup and making their homes safe, region’s beautiful coastlines, bays, hills, to estimate the likelihood of future earth- a task made easier because both groups and valleys is also the primary driving quakes. The Global Positioning System were trained in disaster preparedness force for earthquakes along faults in (GPS) and other land surveying and the clients had emergency with the region. The Bay region is located and geologic techniques have allowed needed supplies on hand. The South within the active boundary between the scientists to make more accurate measure- Napa earthquake shifted houses off their Pacific and the North American tectonic ments of how the current plate motions— foundations, damaged chimneys, started plates, where the slowly totaling 1.6 inches per year across the San fires, and broke water mains throughout and continually slides northwest past Francisco Bay region—distribute stress the city, causing hundreds of millions of the . The San onto these individual faults. Balancing dollars in economic losses. Many historic Andreas Fault, on which two magnitude plate motions with the slip during large masonry buildings in downtown Napa 7.8–7.9 earthquakes have occurred in earthquakes and slow creep on faults allows were damaged. The earthquake was the historical time, including the 1906 San scientists to calculate average rates of earth- largest in the San Francisco Bay region Francisco earthquake, is the fastest quake occurrence over periods of hundreds since the 1989 magnitude 6.9 Loma Prieta slipping fault along the plate boundary. to thousands of years. (Continued on page 4) 2 122°30’ 122°

S A N A N D R E A S Roseville

38°30’ Healdsburg SACRAMENTO Davis

Santa Rosa Vacaville Napa Petaluma Fairfield F A U L T

Novato Vallejo Point Concord 38° Reyes Stockton

San Francisco Bay Oakland San PACIFIC Francisco Hayward Livermore Modesto OCEAN

Half Moon Bay Earthquake San Jose 37°30’ magnitude 1985–2014 2–3 3–4 4–5 Gilroy 5–6 Santa 6.9 Loma Prieta Cruz Watsonville Major faults Monterey Bay 37° Salinas 0 10 20 MILES 0 10 20 KILOMETERS Monterey

Map of earthquakes greater than magnitude 2.0 in the San Francisco Bay region from 1985–2014. Small earthquakes occur on both major faults (shown by the gray lines) and minor faults (not shown). Because of the variability of fault geometry, earthquakes at depth do not always coincide with the mapped faults at the Earth’s surface. There are sections of major faults, particularly the , with few or no small earthquakes but they will produce large earthquakes in the future. Compiled from the Northern California Seismic Network. 3 (Continued from page 2). A trench excavated Calculating accurate earthquake prob- many of the faults in the region. However, across the Hayward Fault in Fremont revealed abilities for short periods, such as 30 years, is the ongoing motion of the tectonic plates evidence of 12 large earthquakes over the past also challenging. Although the 30-year time began rebuilding stresses after the 1906 1,900 years. The time interval between these interval is convenient for humans, it is much event, and earthquakes larger than magni- earthquakes ranged from about 100 to 210 less than the average time between large tude 5.5 resumed during the second half of years. Historical records indicate that the most earthquakes on these faults, which can range the 20th century. Future large, damaging recent large earthquake on this fault occurred from hundreds to thousands of years. The earthquakes in the San Francisco Bay region, in 1868. However, detailed information about rate of large earthquakes in the San Fran- similar in size to the 1989 Loma Prieta and other past earthquakes in the San Francisco cisco Bay region was high in the late 1800s 1906 San Francisco earthquakes, may or may Bay region is difficult to obtain because seis- but dropped abruptly after the 1906 San not be accompanied by the level of earth- mograph records only go back to about 1900, Francisco earthquake on the San Andreas quake activity observed in the late 1800s. historical accounts are sparse before 1850, Fault. Scientists believe that the post-1906 The 2014 Uniform California Earth- and there are limited locations where faults earthquake rate decreased because the large quake Rupture Forecast version 3 (http:// can be trenched to identify and date prehis- amount of slip along the San Andreas Fault pubs.usgs.gov/fs/2015/3009/) provides toric earthquakes. in 1906 temporarily reduced the stress on an updated estimate of the likelihood of large earthquakes in California over a Seven Steps to Earthquake Safety 30-year time window from 2014 to 2043. The forecast accounts for how fast stress PREPARE SURVIVE is accumulating on each fault due to plate Before the next big earthquake we During the next big earthquake, and motions and the time since its most recent recommend these four steps that will make immediately after, is when your level of large earthquake(s). In updating the prob- you, your family, or your workplace better preparedness will make a difference in how prepared to survive and recover quickly: you and others survive and can respond to ability calculations, scientists used a more emergencies: complete set of faults for the San Francisco Bay region than those used in the previous (2008) calculations, adding 32 smaller faults to the 5 major fault systems. The new study has also incorporated more options for how multiple faults might rupture together in large earthquakes.

Step 1: Secure your space by identifying hazards Step 5: Drop, Cover, and Hold On when the earth Probabilities of Earthquakes in the and securing moveable items. shakes. San Francisco Bay Region Smaller earthquakes occur more frequently than larger earthquakes. The probability that an earthquake of magni- tude 6.0 or larger will occur before 2043 is 98 percent. The probability of at least one earthquake of magnitude 6.7 or larger in the San Francisco Bay region is 72 Step 2: Plan to be safe by creating a disaster plan Step 6: Improve safety after earthquakes by percent, and for at least one earthquake of and deciding how you will communicate in an evacuating if necessary, helping the injured, and emergency. preventing further injuries or damage. magnitude 7.0 or larger it is 51 percent. These probabilities include earthquakes on the major faults, lesser-known faults, and RECOVER unknown faults. After the immediate threat of the earthquake has passed, your level of preparedness will The probability of a large earthquake determine your quality of life in the weeks and occurring on an individual fault in the San months that follow: Francisco region is lower than the probabil- ity of an earthquake occurring anywhere in Step 3: Organize disaster supplies in convenient the region. The faults in the region with the locations. highest estimated probability of generat- ing damaging earthquakes between 2014 and 2043 are the Hayward, Rodgers Creek, Calaveras, and San Andreas Faults. In this 30-year period, the probability of an earth- Step 7: Reconnect and Restore. Restore daily life quake of magnitude 6.7 or larger occurring by reconnecting with others, repairing damage, is 22 percent along the San Andreas Fault and rebuilding community. and 33 percent for the Hayward or Rodgers Step 4: Minimize financial hardship by organizing Creek Faults. Individual sections of these important documents, strengthening your Adapted from Seven Steps To Earthquake Safety faults have lower probabilities for large property, and considering insurance. http://earthquakecountry.org/sevensteps/ earthquakes to occur (continued on page 6); 4 122°30’ 122° Maps showing intensity of ground shaking for the South Napa and Loma Prieta earthquakes. The black 1989 Magnitude 6.9 lines show the location of fault Loma Prieta Earthquake slip at depth. The maps illustrate Roseville how the area subjected to strong 38°30’ shaking increases with increasing Healdsburg earthquake magnitude. SACRAMENTO Saint Helena Santa Rosa Vacaville Napa Petaluma

Vallejo Point 38° Reyes Concord Stockton

San FranciscoOakland Bay San Francisco Modesto Hayward

Half Moon Bay San Jose 37°30’ Shaking effects Damage to engineered structures and buildings Road damage from the Loma Prieta Damage to older houses, chimneys, and masonry earthquake. Photograph by H.G. Gilroy Wilshire, U.S. Geological Survey. Objects thrown from Santa Cruz shelves, water sloshed Watsonville

122°30’ Sleepers wakened,122° felt Monterey by almost everybody Bay 37° Felt by some people Salinas 2014 Magnitude 6.0 in tall buildings 0 10 20 MILES

0 10 20 KILOMETERS Monterey South Napa Earthquake Fault rupture Roseville

38°30’ Healdsburg SACRAMENTO

Santa Rosa Vacaville

PACIFIC Napa Fairfield OCEAN Novato Vallejo Point 38° Reyes

San FranciscoOakland Bay San Francisco

0 10 20 MILES 0 10 20 KILOMETERS Fremont Half Moon Damaged building in downtown Bay San Jose Napa. Photograph by Erol Kalkan, U.S. Geological Survey. 37°30’ 5 Additional Earthquake Resources American Red Cross – Bay Area (http://www.redcross.org/local/northern-california-coastal) Association of Bay Area Governments (http://resilience.abag.ca.gov/earthquakes/) Bay Area Earthquake Alliance (http://bayquakealliance.org/) California Earthquake Authority (http://www.californiarocks.com/) California Geological Survey (http://www.consrv.ca.gov/cgs/geologic_hazards/earthquakes) Did You Feel It? (http://earthquake.usgs.gov/earthquakes/dyfi/) Earthquake Country Alliance (http://earthquakecountry.org/) Putting Down Roots in Earthquake Country (http://pubs.usgs.gov/gip/2005/15/) ShakeAlert – An Earthquake Early Warning System for the West Coast (http://pubs.usgs.gov/fs/2014/3083/) ShakeMap (http://www.cisn.org/shakemap/nc/shake/index.html) ShakeOut.org (http://www.shakeout.org/california/bayarea/) Uniform California Earthquake Rupture Fault version 3 Fact Sheet (http://pubs.usgs.gov/fs/2015/3009/) United Policyholders (http://www.uphelp.org/) Damaged building in downtown Napa. Photograph USGS Real-Time Earthquakes (http://earthquake.usgs.gov/earthquakes/map/) by Erol Kalkan, U.S. Geological Survey.

(continued from page 5) however, an Prieta earthquake caused damage over a Before the next earthquake: region nearly 100 miles long. Local soil earthquake of magnitude 6.7 or larger will • Assess your home and work space, and geologic conditions, bedrock type, cause strong shaking over a broad area. identify hazards, and secure moveable quality of building construction, and Therefore, it is important to estimate the items. probability of a large earthquake occurring susceptibility to flooding (caused by dam anywhere in the San Francisco Bay region. or levee failure) can also affect the amount • Create an emergency plan and organize of damage at a particular site. This was disaster supplies to sustain you and your What is the Likelihood That an dramatically demonstrated by the 1989 family for 72 hours or longer. Earthquake Will Affect You? Loma Prieta earthquake, which devastated • Practice “Drop, Cover, and Hold On” to vulnerable parts of Oakland and San protect yourself when the ground begins Francisco, more than 50 miles from the Earthquake probabilities are only one to shake. Learn and practice what to do fault rupture. component in the evaluation of earthquake at home, work, or in school. hazards. Higher magnitude earthquakes have broader areas of intense shaking How Can You Protect Yourself and • Stay prepared by repeating these steps and cause more damage than lower Your Family? on a regular basis. For example, reassess magnitude earthquakes. In a magnitude 6.0 your preparedness every year and earthquake, strong shaking and damage are Taking simple steps before and during participate in the annual Great California confined to a localized area, as illustrated earthquakes can help protect you and your ShakeOut drill on the third Thursday in by the 2014 South Napa earthquake. In family, as well as speed your recovery October. comparison, the 1989 magnitude 6.9 Loma from an earthquake.

Brad T. Aagaard, James Luke Blair, John Boatwright, Susan H. Garcia Ruth A. Harris, Andrew J. Michael, Lack of adequate shear David P. Schwartz, and Jeanne S. DiLeo walls on the garage level exacerbated Edited by Kate Jacques damage to this building and Carolyn Donlin at the corner of Beach For more information contact: and Divisadero in the 1-888-ASK-USGS Marina , San (1-888-275-8747) Francisco, during the October 1989 Loma http://earthquake.usgs.gov/ Prieta earthquake. http://ask.usgs.gov https://www.facebook.com/ USGeologicalSurvey https://twitter.com/USGS

ISSN 2327-6916 (print) ISSN 2327-6932 (online) 6 http://dx.doi.org/10.3133/fs20163020