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Summary of examples of correlation between lithology and seimicity

Summary of examples of correlation between lithology and seimicity. Jessica Hawthorne Ge277 February 26, 2014. Outline. Mostly aseismic with small earthquakes Costa Rica Nankai SAF Zuccale. More clay: M ore velocity-strengthening at low slip speeds Lower absolute strength

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Summary of examples of correlation between lithology and seimicity

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  1. Summary of examples of correlation between lithology and seimicity Jessica Hawthorne Ge277 February 26, 2014

  2. Outline • Mostly aseismic with small earthquakes • Costa Rica • Nankai • SAF • Zuccale

  3. More clay: • More velocity-strengthening at low slip speeds • Lower absolute strength Ikari et. al., 2011

  4. Ikari et. al., 2013 • Northwest: • Cold • Few seamounts • Larger earthquakes • Southeast: • Hot • Seamounts • More small earthquakes Wang and Bilek, 2011

  5. A recipe for small earthquakes? Hemipelagic ooze: Weak, mostly velocity-strengthening Nanofossil chalk on seamounts: Strong, velocity-weakening

  6. Zuccale FaultNiemeijer and Collettini, 2013 • Low-angle normal fault in northenAppenines • Nearby faults have shallow microseismicity • Misorientation suggests low effective friction

  7. Pink and orange: -Less talc, more quartz -More unstable

  8. Less stable deeper • Small earthquakes on velocity-weakening patches

  9. Nankaiaccretionary prism Ikari and Saffer, 2011 • Evidence that splay fault ruptured to the trench • Low frequency earthquakes along splay faults

  10. Ikari and Saffer, 2011 • Mostly velocity-strengthening • Increase in a-b with slip rate mostly results from decrease in b • Suggests it’s hard to rupture seismically

  11. Ujiie and Tsutsumi, 2010 • Strong velocity weakening at higher slip rates • From thermal pressurization

  12. Tsutsumi et. al., 2011 • Some samples are v-w even at low slip rates • Would allow for small earthquakes

  13. San Andreas FaultIrwin and Barnes, 1975 Locations from Waldhauser and Schaff, 2008 Creep and microseismicity coincident with serpentinite at the base of the Great Valley sequence?

  14. Reinen et. al., 1994

  15. So can lithology explain the observed distribution of earthquakes? • Maybe • 4 locations that are consistent, but not compelling • Clays generally stable at low slip speeds • Can be unstable at high slip speeds • Most instability added with more quartz or calcite

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