La DRA. ELIZABETH COCHRAN y tres estudiantes de doctorado de la Universidad de California nos visitan del 10 al 13 de Agosto de 2010.

El Departamento de Sismología del
Instituto de Geofísica de la UNAM

Se complace en invitarlos a la conferencia:

“Imaging Fault Damage Zones with
Seismic and Geodetic Data”
que impartirá la:

DRA. ELIZABETH COCHRAN

Department of Earth Sciences, University of California, Riverside


Martes 10 de agosto a las 12:00 hrs.

AUDITORIO TLAYOLOTL

Edificio Anexo del Instituto de Geofísica
Circuito Exterior, Ciudad Universitaria


Abstract

During earthquakes slip is often localized on preexisting faults, but
it is not well understood how the structure of crustal faults may
contribute to slip localization and energetics. Growing evidence
suggests that the crust along active faults suffers anomalous strain
and damage during large quakes. Data collected along several faults
including the Hector Mine rupture, San Andreas Fault at Parkfield, and
the Calico Fault show damage zones extending from 100 m to 1 km around
the active slip plane. Recent seismic and geodetic data from the
Calico fault in the eastern California shear zone reveal a wide zone
of reduced seismic velocities and effective elastic moduli. Using
seismic travel times, trapped waves, and interferometric Synthetic
Aperture Radar observations, we document seismic velocities reduced by
40 - 50% and shear moduli reduced by 65% compared to wallrock in a
1.5-km-wide zone along the Calico fault. Observed velocity reductions
likely represent the cumulative mechanical damage from past earthquake
ruptures, but can sustain further damage in successive events These
findings indicate that faults can affect rock properties at
substantial distances from primary fault slip surfaces, and throughout
much of the seismogenic zone, a result with implications for the
portion of energy expended during rupture to drive cracking and
yielding of rock and development of fault systems.