Lecture7_2011.knr

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Unformatted text preview: km (could be an 8.6 earthquake) -- The 1857 and 1906 earthquakes were about magnitude 8 -- The San Andreas fault system is more that 1300 km (800 miles) long -- The 9.5 Chilie earthquake had a fault length of ~1000 km -- It is highly unlikely that the entire SAF will rupture - Relatively speaking the SAF is not a very deep fault, in some spots is as much as 16 km (10 miles) deep. The high slip rate (15-25mm/yr), long quiescence (~325 years), and multiple single-event displacements of ~ 2-3 meters, raises concern about the southernmost San Andreas Fault (SSAF) . How to constrain offset Scripps Institution of Oceanography Jeff Dingler Scripps Institution of Oceanography Scripps Institution of Oceanography Ground based LIDAR: Event Offset Scripps Institution of Oceanography Ground based LIDAR: Event Offset Potential Magnitude of the “Big One” ? 174-230 7 5.3 0 1 2 3 4 5 6 F S F S ? 150-269 7 8 9 10 • We have acquired high-resolution seismic data in the Salton Sea, together with onshore Lidar surveys, to define fault architecture and recurrence interval. • The high slip rate (15-25mm/yr), long quiescence (~325 years), and multiple single-event displacements of ~ 3 meters, raises concern about the southernmost San Andreas Fault (SSAF) . • We are defining the sediment character and distribution in the Salton Sea to assess susceptibility to wind erosion (air quality) if portions of the sea are allowed to evaporate. Lake Tahoe Bathymetry Vibra-coring, eastern shoreline inundation age ~19.2 ka Geomorphic Slip-rates On-fault record of deformation Piston coring, deep basin Event Chronology recognized in CHIRP profiles Incline Village Fault W W2 colluvial wedge G2 W TWTT (sec) 3.1m 0.020 10.0 active faults post-MRE sediment Pm 0.015 1.9m Cw 0.9m 13.75 W1 M 1.3m 1.5m W2 pre-MRE sediment (Pm) 0.025 6.25 E ~50m W1 M W2 M 17.5 W1 W1 W2 1.5m W2 0.9m 21.25 W2 ~ 250m W2 ~ 0.030 50m Depth (m) 0.010 Figure 3 0.005 VE ~ 23 25.0 ~50m W2 G W Pm x 3.1m Depth ~7.5 m Cw E post-MRE sediment Inset Photo 1.9m 1.3m Most Recent Event (MRE) deposits 0.9m Boulders MRE deposits Wood Third event deposits Near shore lacustrine deposits x M W1 C14 samples Sedimentary layer 1.5m W1 x x W1 x Fissure x ~ 50m Fault Penultimate deposits x pre-MRE sediment (Pm) Length ~22.5 m Use of dense 3-D grids xx colluvial wedge x W2 Penultimate colluvial wedge deposits x 1 meter (no vertical exaggeration) W2 1.5m W2 0.9m W2 Colluvial Wedge Paleoseismic Trenching Incline Village Elementary School Incline Village Fault Winning the “Geo-lottery” Mega-Tsunami courtesy Dr. Steven Ward 138 Meter Wave Lituya Bay 1720’ run-up West Tahoe Fault v. Genoa Fault New Constraints on Deformation, Slip Rate, and Timing of the Earthquake on the Lake Tahoe Basin 517 Tahoe Hazard Summary Slip-rates on West Tahoe, Stateline/North Tahoe and Incline Village are approximately 0.6-0.8, 0.45 and 0.1-0.2 mm/yr. MR...
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This note was uploaded on 03/23/2012 for the course SIO 35 taught by Professor Driscoll,n during the Winter '08 term at UCSD.

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