Lecture7_2011.knr

Lecture7_2011.knr -...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: http://scrippseducation.ucsd.edu/faculty/driscoll/water Water Cycle Evaporation, Precipitation, and Atmospheric circulation Tectonics and Orographic Effects Fresh Water is 3% What drives the plates? Tectonics - regulates circulation Percolation Mount Soledad Rose Canyon Fault JUNTO Talk Mount Soledad October 3, 2007 Slide Slide courtesy of Ken Melville Scripps Institution of Oceanography Scripps Institution of Oceanography ~ 50 mm/yr Scripps Institution of Oceanography Scripps Institution of Oceanography Scripps Institution of Oceanography Large Historic Earthquakes, California Fort Tejon Earthquake, January 9th, 1857 Lone Pine Earthquake, March 26th, 1872 M 7.6-8.0, 27 Dead, 4-5 m vertical, 10-15 m lateral M 7.9, 2 Dead, 6 m lateral, 9 m lateral Great San Francisco Earthquake, April 18th, 1906 M 7.8, 3000+ Dead, 6 m lateral, 8.5 m lateral at depth Loma Prieta Earthquake, October 17th, 1989 aka World Series Earthquake M 6.9, 63 Dead, 4000 injured Northridge Earthquake, January 17th, 1994 M 6.7, 72 Killed, 9000 injured, highest measured g Future Catastrophe? M7.8+ M6.7+ M7.3 West Tahoe Fault San Andreas Fault Hayward Fault Stanford’s Past Catastrophe! San Jacinto Fault M7 M7 Wasatch Fault Sierra Nevada Microplate nd Blanco M M Me Fracture Fracture Zone JUAN DE FUCA PLATE o o oc ino ac Fr s ca Ca n tio uc bd Su Z r re tur GORDA PLATE dia Ore gon n Zo Co e ast blo ck on e e e PACIFIC PLATE MTJ KLAMATH MOUNTAINS ˚ 45 SEGP 5˚ 12 HC W ICF N ND AN R R RA E SNFFS G G NG Lane LV belt San Andreas Fault Understanding California Tectonics and Earthquakes Hazards I I IN Walker C 40 FLV-FC-DV I OV IWV ˚ ECSZ 115 ˚W 11 0˚ W 12 0˚ W S BA MV HL T SIERRAN MICROPLATE Walker Lane 35 ˚ GPS across the “Basin and Range” Plate Reconstruction of the Californias Scripps Institution of Oceanography Scripps Institution of Oceanography Scripps Institution of Oceanography Stress and Strain Earthquake Size • Fault Geometry and the Size of an Earthquake ◦ the magnitude of an EQ depends on the fault (or rupture area) geometry ◦ magnitude scales with area of fault plane (or more precisely, rupture area) and the slip ◦ larger EQs last longer (e.g. small EQs shake a few seconds but the large 04 Sumatra EQ shook for 10min) ◦ larger EQs have typically larger horizontal slip ◦ larger EQs also have larger rupture lengths (the distance along a fault over which the slip occurred) ◦ the longer a fault is, the larger an EQ it is potentially capable of ◦ short faults are therefore unlikely to produce large EQs Earthquake Recurrence Interval and Offset Seismic CHIRP Profiling Trenching Event Chronology Lidar Sediment Coring ... 840 AD, 1000 AD, 1231 AD, 1502 AD, 1680 AD...The Big One (330 years and counting...) Stratigraphy is the tape recorder of Earthquakes. More continuous record offshore and in lakes. The Tale of Two Lakes Salton Sea West Tahoe Fault, M7.3 Southern San Andreas M 7.8+ Lake Tahoe Lake Cauhilla TeraShake Project October 15, 2009 Brawley Seismic Zone ‘Xplained Brothers et al., 2009 Salton Soup First CHIRP data from the Salton Sea Scripps Institution of Oceanography Perks of the Job Salt Creek Trench Salt Creek Trench Lake Cahuilla Stratigraphy Expected Stratigraphy Beneath the Salton Sea (Based on Philibosian’s model) Sequences separated by transgressive surfaces A’ A Coachella Site (9 m) High-stand (13 m) Elevation (m) 0 A 20 40 60 A’ Salton Sea (-70 m) 80 L6 0 40 80 120 Distance (km) 160 Lake 6 Deep water deposits 200 240 Building a Stratigraphic Framework Beneath the Salton Sea A’ A Coachella Site (9 m) High-stand (13 m) Elevation (m) 0 A 20 40 60 A’ Salton Sea (-70 m) F6 L6 80 0 40 80 120 Distance (km) 160 Short separation in high-stands Lake remains deep 200 240 Building a Stratigraphic Framework Beneath the Salton Sea A’ A Coachella Site (9 m) High-stand (13 m) Elevation (m) 0 L5 F6 L6 A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) 160 Lake 5 Deep water deposits 200 240 Building a Stratigraphic Framework Beneath the Salton Sea A’ A Coachella Site (9 m) High-stand (13 m) Elevation (m) 0 F5 L5 F6 L6 A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) 160 150 year hiatus Shallow water/fluvial deposits 200 240 Building a Stratigraphic Framework Beneath the Salton Sea A’ A Coachella Site (9 m) High-stand (13 m) L4 F5 L5 F6 L6 Elevation (m) 0 A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) 160 Lake 4 Deep water deposits 200 240 Building a Stratigraphic Framework Beneath the Salton Sea A’ A Coachella Site (9 m) High-stand (13 m) F4 L4 F5 L5 F6 L6 a 0 a Elevation (m) a A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) 160 180 year hiatus Shallow water/fluvial deposits Very distinct in trench 200 240 Building a Stratigraphic Framework Beneath the Salton Sea A’ A Coachella Site (9 m) High-stand (13 m) L3 F4 L4 F5 L5 F6 L6 a 0 a Elevation (m) a A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) 160 Lake 3 Deep water deposits 200 240 Building a Stratigraphic Framework Beneath the Salton Sea A’ A Coachella Site (9 m) High-stand (13 m) F3 L3 F4 L4 F5 L5 F6 L6 a 0 a Elevation (m) a A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) 20 year hiatus Shoreline regression Subtle change 160 200 240 Building a Stratigraphic Framework Beneath the Salton Sea A’ A Coachella Site (9 m) L2 F3 L3 High-stand (13 m) F4 L4 F5 L5 F6 L6 a 0 a Elevation (m) a A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) 160 Lake 2 Deep water deposits 200 240 Building a Stratigraphic Framework Beneath the Salton Sea Coachella Site (9 m) High-stand (13 m) L4 F5 L5 F6 L6 a 0 a Elevation (m) a F4 A’ A F2 L2 F3 L3 A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) 30 year hiatus Shoreline regression Subtle change 160 200 240 Building a Stratigraphic Framework Beneath the Salton Sea Coachella Site (9 m) High-stand (13 m) L4 F5 L5 F6 L6 a 0 a Elevation (m) a F4 A’ A L1 F2 L2 F3 L3 A 20 40 60 A’ Salton Sea (-70 m) 80 0 40 80 120 Distance (km) 160 Lake 1 Deep water deposits 200 240 Building a Stratigraphic Framework Beneath the Salton Sea 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) 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 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. MRE age on West Tahoe Fault, 4.1-4.5 ka; Incline Village Fault, 0.6 ka; Stateline/North Tahoe Fault, Holocene. Size of MRE rupture: West Tahoe Fault, ~3.7-4.1 m; Incline Village, ~3-3.5 m; Stateline/North Tahoe, unknown. Total extension across basin is ~0.5 mm/yr. sedimentation rate extrapolation suggest ~60 ka age of slide, maybe younger. ~2000-3000 year potential recurrence interval for tsunami-generating M7 earthquake. West Tahoe Fault: ~55 km length has a potential of a M7.3 rupture. Figure 19. Comparison of the West Tahoe fault and the GF; both faults exhibit similar range front morphology, strike, and length. Together, these faults appear to be accommodating most of the extension (2–3 mm=yr) occurring within the northern Walker Lane at the latitude of Lake Tahoe. second method, the offset fan surface offshore Sugar Pine Point (Figs. 16 and 18) is presumed to be inactive since the Tioga glacial retreat (Dingler, 2007). The 10.5 m offset (Fig. 18) since 13 k.y. B.P. also produces a maximum vertical slip rate of ∼0:8 mm=yr. Overall, these data give rise to a vertical displacement rate between 0.4 and 0:8 mm=yr since the end of Tioga glaciation, which is slightly higher than the 0:5 mm=yr minimum slip-rate estimate (over the last ∼20 ka) reported by Kent et al. (2005). An extension rate can be estimated from vertical slip rate assuming simple fault geometry. For a 60° dipping normal fault, the vertical deformation rate is transformed into an extension rate between 0.3 and 0:5 mm=yr. The slip rate along the WTDPF may be higher than estimated because the MRE occurred at 4.1– 4.5 k.y. B.P. and, presumably, additional strain has accumulated during the quiescent interval. With a slip rate between 0.4 and 0:8 mm=yr, it is possible that ∼3 m of elastic strain has accumulated across the WTDPF. Coseismic slip of 3 m on the WTDPF could generate an M ≥ 7 event. The GF (Fig. 19) has a vertical deformation rate of 2–3 mm=yr over the last 2 k.y. (Ramelli et al., 1999), which can be converted to a 1:2–1:7 mm=yr extension rate (also assuming 60° dip). The combined extension rates of the GF and the WTDPF are consistent with the 2–3 mm=yr GPS derived extension rates across the Sierra Nevada frontal fault zone (Hammond and Thatcher, 2004, 2007). Earthquake triggering associated with normal fault earthquakes and resulting static stress changes have been used to explain normal fault event sequences (Nostro et al., 1997); therefore, it is important to compare paleoearthquake records between neighboring faults. Events on the IVF and GF at ∼500 yr B.P. (Ramelli et al., 1999; Dingler, 2007) suggest a possible relationship in the rupture timing, but the age uncertainty is large and coincident timing could also be re- Persistent Drought—60% of “normal”, Medieval Period Rooted Trees 110’ Submersible Cedar Grove Cryptomonads Submersible Onshore and Offshore Mapping Scripps Institution of Oceanography Onshore and Offshore Mapping Liz Johnstone Scripps Institution of Oceanography Complex Bluff Geometry in Northern Solana Beach • I-Site Studio Software • Spherical Triangulation • Overhang Modeling Solana Beach Bluff Failure September 28, 2004 Before After May 12, 2004 September 28, 2004 Erosion and Accretion Areas of Failure Failure Volume 890 m3 ± 3% -4.0 0.0 Change (meters) 4.0 Scripps Institution of Oceanography Scripps Institution of Oceanography Scripps Institution of Oceanography Scripps Institution of Oceanography Scripps Institution of Oceanography Scripps Institution of Oceanography Seafloor and Subsurface Mapping Central Lobe Scripps Institution of Oceanography Seafloor and Subsurface Mapping Scripps Institution of Oceanography Scripps Institution of Oceanography Leah Hogarth Scripps Institution of Oceanography Rose Canyon Fault Offshore pop-up structure Seafloor and Subsurface Mapping midshelf wedge Transgressive surface Scripps Institution of Oceanography Seafloor and Subsurface Mapping Scripps Institution of Oceanography Seafloor and Subsurface Mapping midshelf wedge Transgressive surface Scripps Institution of Oceanography Seafloor and Subsurface Mapping The observed sediment thicknesses suggest sea level fluctuations and tectonics controls long-term sediment accumulation in the region and hydrodynamics controls sediment dispersion (Hogarth et al., 2007). Scripps Institution of Oceanography Scripps Institution of Oceanography Tectonic Deformation • controls landscapes and seascape evolution • resources - hydrocarbons and sand • Geohazards - earthquakes, slope failures, tsunamis • Biohabitats - through exposure of different lithology (rock types) Scripps Institution of Oceanography Scripps Institution of Oceanography Scripps Institution of Oceanography ...
View Full Document

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.

Ask a homework question - tutors are online