Presentation on theme: "Seismic and Tsunami Threats to Southern California Nancy King, Ph.D. U.S. Geological Survey Pasadena Field Office Northridge earthquake 1994 Northridge."— Presentation transcript:
Seismic and Tsunami Threats to Southern California Nancy King, Ph.D. U.S. Geological Survey Pasadena Field Office Northridge earthquake 1994 Northridge earthquake, 1994 Emergency Response Readiness Workshop Joint Forces Training Base, Los Alamitos, California May 10, 2012
Faults and Plate Tectonics Plate motion occurs on faults.
What Faults Look Like After Earthquakes 1906 San Francisco earthquake 1979 Imperial Valley earthquake Scarp of 1971 San Fernando earthquake Photo from Finding Fault in California: An Earthquake Tourists’ Guide, by Susan Elizabeth Hough Landers earthquake, 1992
Faults and Shaking An earthquake is sudden slip on a fault. This slip triggers seismic waves. These waves cause shaking and most of the damage.
What the San Andreas Fault Looks Like Stream offset: 420 feet in 3800 years
Faults of Southern California Over 300 faults in Southern California Only the San Andreas can have the “Big One” (M 7.8+) But earthquakes on other faults can be disasters, e.g. 1994 Northridge M 6.7 But other faults can produce damaging earthquakes
Magnitude and Intensity Magnitude is the maximum amplitude on a seismogram. Worldwide neic.usgs.gov/neis/eqlists/eqstats.html Doug Given, USGS The magnitude scale is logarithmic. Each whole number increase is: 10 times more ground motion 32 times more energy Intensity is the earthquake’s effects, on scale of I to XII. Depends on: Distance from earthquake Geology Type of structure Observer! Varies from place to place.
Earthquakes in California 19302007 50,000 Good seismic network begins here. On average in southern California: Over 30 per day, mostly not felt Magnitude 6 every 5 years Magnitude 7 every 30 years Magnitude 7.7 every 150 years We CANNOT predict these earthquakes!
Earthquake Effects – Aftershocks March 11, 2011 Tohoku M 9.0 earthquake and its aftershocks in the first day
Earthquake Effects - Structure Failure Ferndale, CA, M 7.1 1992 Life-safe Columbia, M 6.2, 1999 NOT life-safe Northridge, CA, M 6.7 1994 Performance depends on Material Construction
Earthquake Effects - Utility Line Rupture USGS Open File Report 96-263 Northridge earthquake,1994
Earthquake Effects - Lifelines Highways, railways, power lines, phone lines, pipelines, and water aqueducts and pipelines all cross the San Andreas fault
Earthquake Effects - Interior Damage Dr. Cindy Stern
Earthquake Effects – Landslides and Liquefaction Landslides – Northridge, 1994 Steinbrugge Collection of the UC Berkeley Earthquake Engineering Research Center Liquefaction – Niigata, Japan, 1964
Earthquake Effects - Tsunamis One or more intense waves, usually caused by an earthquake or undersea landslide. First wave may NOT be the largest. Timing between waves may vary from minutes to several hours apart. The danger lasts hours after the first wave. Tsunami waves can come ashore in different ways: Wall of water – rapidly rising tide – series of surf-like breakers Tsunamis can carry boats, debris and heavy rocks. Types: Local – earthquakes near the coast where first wave can be within 10 minutes and may not be time for a tsunami warning Pacific-wide – caused by earthquakes far away from our coast which allows time for an tsunami warning Vulnerable areas in so. California include: LA and Long Beach Harbor, Venice and West Los Angeles beaches. TSUNAMI WARNING BROADCAST: Pack up your family and pets and move inland
Earthquake Effects - Community Death and injury Structure damage No power/gas Fire No water Road/rail closures Phones out No emergency services Stranded commuters Separated families Destroyed homes Stores closed Business losses Loss of jobs
The Big One The last Big One in southern California was the Fort Tejon Earthquake of 1857, which killed 2 people. No one remembers this earthquake. The next Big One will be different, causing casualties and damage in now heavily populated southern California. There will be up to 2 minutes of ground shaking. Preparation and response are local. It’s up to us.
Earthquake Deaths Roger Bilham, University of Colorado Japan 2011
Earthquake Preparedness and Response Retrofit buildings Secure fixtures/contents Emergency plan Emergency supplies Check for damage and injuries Follow your emergency plan Expect aftershocks Contact insurance agent Restore documents Begin repairs Contact FEMA Before During – Drop, cover, and hold on! After
USGS Products CISN Display – Real time earthquake alert and notification California-Nevada Earthquake Map Earthquake Notification System ShakeCast – Situational awareness tool for emergency responders and critical facility operators