Kenneth W. Hudnut USGS, Pasadena, CA West Newport Beach Association Public Forum, Newport Beach City Hall March 5, 2003 Coping with ‘quakes

What is an earthquake? Sudden slip of one block of rock across another Produces shaking as one of its effects The shaking is what you feel

Earthquakes are driven by plate tectonic motion As the Farallon plate subducted, the San Andreas fault was born In the past 5 million years, this motion has been steady at about 2 inches per year (that’s 15 feet per century or 30 miles per million years!) Movie by T. Atwater, UCSB

Earthquakes are driven by plate tectonic motion In the past 5 million years, this motion has been steady at about 2 inches per year (that’s 15 feet per century or 30 miles per million years!) Yes, LA will be in San Francisco No, LA will not fall into the sea Movie by T. Atwater, UCSB

Earthquake Terminology Strike-slip Faults Rupture surface Hypocenter Hypo- center Epicenter Fault plane Fault

strike-slip - Hector Mine (M w 7.1) Photo by Paul ‘Kip’ Otis-Diehl, USMC, 29 Palms

‘A rip in the desert canvas’ - Los Angeles Times Katherine Kendrick, USGS Chris Walls, Earth Consultants International

What Controls the Level of Shaking? Magnitude – More energy released Distance – Shaking decays with distance Local soils – Amplify the shaking

Undamaged buildings on the fault 1906 San Francisco

Damage at great distance The Bay Bridge 1989 Loma Prieta The Marina District

Probabilistic Seismic Hazard Analysis Determine the rate of earth- quakes Probable earthquake forecast for 30-year time frame for the southern California region

California has many faults! San Andreas fault carries about 2/3 of the plate boundary motion Faults such as the Newport-Inglewood and ‘blind thrust’ faults also pose significant hazards

Los Angeles metro region faults The Newport- Inglewood (NIF) is one of many faults that pose hazard to Newport Beach NIF has been seriously considered as a potential source for a devastating earthquake

Newport-Inglewood fault Killed 120 people in the 1933 earthquake; 70th anniversary next Monday Oil production from six fields led to very detailed mapping and subsurface imaging

San Joaquin Hills fault Grant et al. - suggested on basis of deformed and uplifted marine terraces Hazard impact is uncertain but official hazard maps will attempt to include it in future revisions

Living with earthquakes without prediction Build to withstand earthquakes Earthquakes don’t kill people—buildings do Evaluate earthquake rates “Climate” not prediction State-of-the-Art Earthquake Monitoring Improve earthquake response Earthquake early warning

CISNCISN A network of ground motion sensors A cooperative project between : U. S. Geological Survey California Institute of Technology California Division of Mines and Geology

The SCIGN array uses GPS to measure the buildup and release of strain on the fault system in southern California

Improved response Post-disaster mitigation Reducing actual losses – Fires – Aftershocks and foreshocks – Search and rescue

EarthScope and ANSS CISN and SCIGN in SoCal (since 1994 Northridge earthquake) are state-of-the-art arrays Prototypes for deployment at large- scale in ANSS and EarthScope

For additional information – Arthur C. Clarke's 2 nd Law: "The only way of discovering the limits of the possible is to venture a little way past them into the impossible." USGS photo by John Galetzka