Lecture7_2011.knr

Water deposits 200 240 building a stratigraphic

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Unformatted text preview: A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) Dry to very shallow lake 1720 - 1905 160 200 240 Building a Stratigraphic Framework Beneath the Salton Sea SS F1 L1 F2 L2 F3 L3 Coachella Site (9 m) High-stand (13 m) L4 F5 L5 F6 L6 a 0 a Elevation (m) a F4 A’ A A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) Salton Sea 1905 - present 160 200 240 Along-strike CHIRP profile Salton Sea Brothers et al., 2009 Close-up View: Hinge Zone “When the dog bites, when the bees sting” March 2009 M 4.8 swarm (blue); 2001 (red) Elmore Ranch— Superstition Hills November 24, 1987 Hudnut et al. 1989 Implications for Southern San Andreas ... 840 AD, 1000 AD, 1231 AD, 1502 AD, 1680 AD...The Big One (330 years and counting...) 7 major events on all three normal faults, 5 of which occurred during flooding of Lake Cahuilla and 3 maybe 4 are coincident with events on the Southern San Andreas How Are Large Earthquakes and Lake Cycles Related? What does it mean if there really is a connection between the lakes and eqs? Perhaps a ranked priority of what to consider in estimating seismic hazard K larson study for thesis in 1990 did elastic halfspace and decided no Hawaiian Islands Stress and Strain Lake Loading TerraShake Model for ground shaking Scripps Institution of Oceanography Hypothesis: Lake change triggers deep lake faults, which in turn trigger the Southern San Andreas Fault. What does it mean if there really is a connection between the lakes and eqs? Perhaps a ranked priority of what to consider in estimating seismic hazard K larson study for thesis in 1990 did elastic halfspace and decided no Summary • • •Phone not off •Important to quantify our Uncertainties •Dynamic stresses are important in earthquake triggering Capture of the Colorado River and consequent Lake Cahuilla flooding provides optimal conditions for triggered rupture on faults beneath the lake and subsequent triggering on the southern San Andreas Fault. The static stress changes from lake loading (0.05 - 0.2 MPa) and stress changes from rupture on faults below the Salton Sea (up to 1.4 MPa) are sufficiently high enough to affect the state of stress on the Southern San Andreas Fault. Ph ot o fr o m: htt p:/ / w w w. str an ge co s m os .c o m/ im ag es/ co nt en t/ 14 18 80 .jp g 4 2 7 10 9 3 8 6 1 5 Largest Earthquakes 1. 2. 3. 4. 5. -- Haiti at magnitude 7.0 isn’t even on the list (it is number 343) -- Top 100 7.8 and larger -- Top 200 7.4 and larger -- We have ~15-20 magnitude 7 or greater earthquakes per year -- Rupture length of an 8.6 earthquake is ~500 km == 310 miles long -- Distance from San Diego to San Francisco = 500 miles = 800 km Chile Alaska Indonesia Kamchatka Chile 1960 1964 2004 1952 2010 M9.5 M9.2 M9.1 M9.0 M8.8 6. 7. 8. 9. 10. Ecuador Alaska Indonesia Tibet Alaska 1906 1965 2005 1950 1957 M8.8 M8.7 M8.6 M8.6 M8.6 Image from Dr. Smith (IGPP/SIO) -- Distance from San Diego to parkfield == 310 miles == 500...
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