[ghsc-seminars] GHSC Seminar Tuesday, April 3rd @ 2pm: Thorne Lay, UCSC

[Mirus, Benjamin]

*"Resolving the up-dip extent of slip in large subduction zone earthquakes
and its influence on aftershock distributions"*

*Thorne Lay*
*UC Santa Cruz*

​Slip distributions during large underthrusting earthquakes on subduction
zone plate boundaries are now commonly determined using seismic, geodetic,
and/or tsunami observations. A persistent challenge has been to constrain
the up-dip extent of rupture, or how close to the trench coseismic sliding
occurs. This issue is important for several reasons. Assessing the
potential for shallow tsunami earthquakes that rupture the megathrust near
the trench requires knowledge of whether prior deeper ruptures have
extended to the trench.  This is illustrated by the 2010 Mentawai tsunami
earthquake, which ruptured up-dip of the 2007 Sumatra event.  Earthquake
slip at shallow depth also characterizes the frictional properties of the
shallow megathrust and its seismogenic potential. On-land geodetic
observations have little resolution of rupture if it occurs relatively far
off-shore, as was demonstrated by analyses of the great 2011 Tohoku
earthquake. Seismological observations alone also may have quite limited
resolution of very shallow faulting on the up-dip portion of the
megathrust. New approaches using water reverberations in the P coda hold
promise of improving seismological resolution. Off-shore seafloor geodetic
observations (GPS-Acoustic or ocean-bottom pressure sensors) significantly
improve the determination of trenchward rupture extent, as shown for the
2011 Tohoku event, but only a few regions currently have sufficient
instrumentation. For a number of recent large earthquakes, joint analysis
of seismic and tsunami observations, in some cases including on-shore and
off-shore geodetic data, appears to provide reliable estimates of up-dip
slip extent (corroborated by direct imaging of seafloor offsets for 2010
Maule, Chile and 2011 Tohoku earthquakes). For the tsunami data to be best
interpreted, corrections for path effects that have commonly been ignored
must be included.

*Tuesday, April 3rd**, 2018*
*​2​*
*-*
*3​pm*
*​  (Mountain Time)*
*USGS, 1711 Illinois Street, Golden, CO*
*Entry Level Seminar Room*

*Note: Please arrive *~5 minutes early* and *bring photo ID* for
airport-style security measures now in place at the USGS building.

Thank you,
GHSC Seminar Committee

Mirus, Ben - bbmirus at usgs.gov
Josh Rigler - erigler at usgs.gov
Oliver Boyd - oboyd at usgs.gov

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