Annual Meeting - SCEC.org

Poster Abstracts
most of the northern Borderland from Point Arguello to the southern San Diego Trough offshore Baja California. The second
area covers the northern part of the Inner Borderland and eastern Outer Borderland from San Nicolas Island to Oceanside
centered around Catalina Basin and Santa Catalina Island. The third area covers the northern Outer Borderland, south of the
Channel Islands and south of the San Nicolas Island escarpment. The fourth area covers the central Outer Borderland from
San Nicolas Island to Velero Basin west of northern Baja California. New multibeam bathymetry tracklines were chosen to
follow major seafloor escarpments where active faulting is expressed by scarps and other lineaments in the seafloor
morphology. Area 2 (Catalina) provides coverage of the major San Clemente fault system including triple junctions (fault
wedge tips of Crowell, 1974) where major active faults intersect at each end of the Catalina Ridge. Area 3 (North Ferrelo)
provides coverage of the major Ferrelo fault zone that extends to the southeast from Santa Rosa Island for more than 300-km
into Mexican waters. The northern section of the East Santa Cruz Basin fault zone (ESCB) lies within the third area. Area 4
(South Ferrelo) provides coverage of the southern two-thirds of the Ferrelo fault zone that lies within U.S. waters–existing data
provide some coverage of this fault zone in Mexican waters to the south. The southern sections of the ESCB fall within the
South Ferrelo map area. The transverse San Nicolas Island escarpment is covered by both Ferrelo map areas, with the southern
map providing coverage of the intersection with the ESCB to the east and the northern map covering the intersection with the
Ferrelo fault zone to the west. In preliminary analysis, we have identified numerous seafloor channels inferred to result from
turbidite flows and deposition that may provide important piercing points where active faults are crossed, such as the San
Diego Trough and San Pedro Basin fault zones.
SURFACE RUPTURE AND SLIP VARIATION INDUCED BY THE 2010 EL MAYOR – CUCAPAH
EARTHQUAKE, BAJA CALIFORNIA, QUANTIFIED USING COSI-CORR ANALYSIS ON PRE- AND POST-
EARTHQUAKE LIDAR ACQUISITIONS. (A-044)
S. Leprince, K.W. Hudnut, S. Akciz, A. Hinojosa Corona, and J.M. Fletcher
One-hundred and three years after the publication of the Lawson report on the Great 1906 earthquake, accurate
documentation of surface deformation along the entire length of an earthquake is still challenging. Analysis of pre- and postearthquake
topographic data provides an opportunity to deliver the full 3D displacement field of the ground’s surface.
However, direct differencing of a pre- and post-earthquake digital topography model (DEM) generally leads to biased
estimation of the vertical component of the deformation. Indeed, if the earthquake also produced significant horizontal motion,
or if the pre- and post-earthquake DEM acquisitions exhibit non-negligible horizontal mis-registration, the vertical offset
measured by direct differencing will be biased by the local topography gradient. To overcome this limitation, we use the
COSI-Corr sub-pixel correlation algorithm to estimate the relative horizontal offset between the pre- and post- 2010 El Mayor –
Cucapah earthquake high resolution LiDAR acquisitions. Compensating for the horizontal offset between the two LiDAR
acquisitions allows us to estimate unbiased measurements of the vertical component of the surface fault rupture induced by
the El Mayor – Cucapah earthquake. We will also show the limitations of the available dataset, such as aircraft jitter artifacts,
which impaired accurate measurements of the horizontal component of the surface deformation. This analysis shows an
unprecedented view of the complete vertical slip component of the rupture induced by the Mw 7.2 2010 El Mayor – Cucapah
earthquake, sampled at every 5 m, over a length of about 100 km, and with a vertical accuracy of a few centimeters. Using
sampling bins as narrow as 150 m and 1.5 km long, variations in the vertical component of an oblique slip earthquake are
presented, with breaks along multiple fault-strands showing opposite dip directions and diffuse boundaries. Vertical
displacement profiles across the entire fault rupture and selective horizontal displacement profiles will be shown. With the
availability of high precision pre- and post-earthquake data, COSI-Corr has the ability to accurately document the variability
of 3D surface slip along strike of an earthquake rupture. Such data can be used to investigate the causes of this variability, and
improve our understanding of its influence on the pattern of ground shaking.
http://www.tectonics.caltech.edu/slip_history/spot_coseis/
PRELIMINARY EVALUATION OF THE 2010 SHAKEOUT EARTHQUAKE DRILL (A-025)
A. Leslie, L.A. Davis, M.M. Wood, and R. Green
An annual ShakeOut earthquake drill has been held in California since 2008. Evaluation of such efforts is essential to
confirming successful implementation, assessing program effectiveness, and determining whether resources have been used
efficiently. Evaluation activities have taken place for each of the ShakeOuts to date. Following the most recent ShakeOut in
October of 2010, an internet survey was conducted with registrants 3 -7 weeks following the drill. A volunteer sample
(N=1,879 of 8,726 registrants with valid email addresses; 22%) of registered ShakeOut participants was recruited to participate
in the survey via email. The survey sample consisted of respondents who were California residents who were registered as
194 | Southern California Earthquake Center