1 / 18

Earthquake triggering

Earthquake triggering. Schuyler Ozbick. The trigger. http://www.eqecat.com/catwatch/virginias-m-5-8-wake-up-call-2011-09-07/. The trigger. Triggered earthquakes can be seen at distances larger than a regional fault network

kalei
Download Presentation

Earthquake triggering

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Earthquake triggering Schuyler Ozbick

  2. The trigger http://www.eqecat.com/catwatch/virginias-m-5-8-wake-up-call-2011-09-07/

  3. The trigger • Triggered earthquakes can be seen at distances larger than a regional fault network • They can also occur anytime between seconds and decades after the initial earthquake in the sequence

  4. Coulomb Stress Coulomb failure criterion Coulomb stress = shear stress – friction coef. (normal stress-pore fluid P) Fault brought closer to rupturing if shear stress is increased or the effective normal stress is decreased.

  5. Coulomb Stress Changes in Coulomb stress for a vertical strike-slip fault where green represents no change in stress

  6. 1933 Long Beach sequence • 1933 Long Beach. M= 6.4 • 1952 Kern Country California. M= 7.3 • 1971 San Fernando. M= 6.7 • 1994 Northridge. M= 6.7 http://content.cdlib.org/ark:/13030/kt8p3014k2/

  7. 1933 Long Beach sequence • 1933 Long Beach. M= 6.4 • 1952 Kern Country California. M= 7.3 • 1971 San Fernando. M= 6.7 • 1994 Northridge. M= 6.7 http://www.ngdc.noaa.gov/hazardimages/picture/show/109

  8. 1933 Long Beach sequence • 1933 Long Beach. M= 6.4 • 1952 Kern Country California. M= 7.3 • 1971 San Fernando. M= 6.7 • 1994 Northridge. M= 6.7 http://earthquake.usgs.gov/earthquakes/states/events/1971_02_09_photos.php

  9. 1933 Long Beach sequence • 1933 Long Beach. M= 6.4 • 1952 Kern Country California. M= 7.3 • 1971 San Fernando. M= 6.7 • 1994 Northridge. M= 6.7 http://www.flickriver.com/places/United+States/California/Los+Angeles/Northridge/search/

  10. Rainbow Mountain sequence • July 6, 1954 at south end of Rainbow Mountain fault • August 24, 1954 along Rainbow Mountain fault • December 16, 1954 at Fairview peak • December 16, 1954 at Dixie Valley • (4 min 30 sec later) • March 29, 1959 south end of Dixie Valley fault • June 23, 1959 in SW Fairview Peak region

  11. Rainbow Mountain sequence bssa.geoscienceworld.org

  12. Landers-Big Bear sequence • April 1992 Joshua Tree quake of M=6.1 • June 1992 Landers quake of M=7.3 • The Landers quake caused increased seismic activity in ranges from a few meters to beyond 1000 km and triggered many small (M=1-3) events

  13. Landers-Big Bear sequence • Joshua Tree and Landers earthquakes created a new positive Coulomb stress change pattern • The Big Bear earthquake was triggered 3.5 hours after Lander quake. • Big Bear earthquake M=6.3

  14. Landers-Big Bear sequence • After the Big Bear quake, the Coulomb stresses were altered. After Big Bear Before Big Bear

  15. Landers-Big Bear sequence • April 1992 Joshua Tree quake of M=6.1 • June 1992 Landers quake of M=7.3 • June 1992 Big Bear quake of M=6.3 • 3.5 hours after Landers • October 1999 Hector Mine quake of M=7.1

  16. Trigger Happy • Does this earthquake belong to a sequence? • Was it triggered by a previous earthquake? • What does the time delay suggest? • Redistributed stress postseismatically by relaxation, rebound and afterslip? • Does it conform to an increased Coulomb stress? • Disagreements over stress shadows

  17. Trigger Happy Coulomb stress and observed aftershocks of Homestead Valley earthquake of 1979 M=5.5

  18. References • Earthquake triggering by static, dynamic, and postseismic stress transfer, Andrew M. Freed, Annu. Rev. Earth Planet. Sci. 2005 33:335-67 • Earthquake processes in the Rainbow Mountain-Fairview Peak-Dixie Valley, Nevada, region 1954-1959, Diane I. Doser, Journal of Geophysical Research, vol 91 no. B12 pg. 572-586, Nov 1986 • Delayed triggering of 1999 Hector Mine Earthquake by viscoelestic stress transfer, Andrew M. Freed and Jian Lin, Nature vol 411 pg 180-181, May 2001

More Related