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Report | SCEC Research Accomplishments
Research Accomplishments
Southern California Earthquake Center
2011 Annual Report
This section summarizes the main research accomplishments and research-related activities during 2009 and the early months
of 2010. The research reported here was funded by SCEC with 2010 research funds. While the presentation is organized
sequentially by disciplinary committees, focus groups, and special project working groups, it is important to note that most
SCEC activities are crosscutting and could be presented under multiple focus groups.
Disciplinary Activities
The following reports summarize recent progress in the three main infrastructural activities and the discipline-oriented
research, Seismology, Geodesy, and Geology.
Seismology
The objectives of the Seismology group are to gather data on the range of seismic phenomena observed in southern California
and to integrate these data into physics-based models of fault slip. Researchers investigate seismicity across the network of
southern California faults to explore spatial and temporal distribution of earthquakes and tremor, associated stress drops, and
triggering etc. New methods are being developed to search for unusual signals using combined seismic, GPS, and borehole
strainmeter data. In addition, near-fault crustal properties, fault structural complexity, and constraints on crustal structure and
the state of stress are being explored. The seismology group is committed to the enhancement and continued operation of the
SCEDC and other existing SCEC facilities particularly the near-real-time availability of earthquake data from SCEDC and
automated access. Related work includes the enhancement of capability for earthquake early warning (EEW) systems and
densification of seismic instrumentation. Below we highlight a subset of the recent research accomplishments.
Seismicity Studies
Figure 1. Major earthquake swarms in the Salton Trough since 1981. Examples
of estimated seismicity migration vectors are plotted in red. These generally
trend SW– NE at velocities of 0.1 to 0.5 km/hr.
Shearer and Hauksson are producing an updated relocated reference catalog
that will include accurate error estimates. More than 500,000 earthquakes are
included between 1981-2010. The effort required the development of new
analysis methods to mine efficiently the large dataset. Shearer et al. also
explored major earthquake swarms that occurred in the Salton Trough since
1981. They found that swarms typically last 1-20 days and that seismicity
during a swarm migrates with time. Analysis of the migration shows that
swarm migrations typically trend SW-NE at a rate of 0.1 to 0.5 km/hr (Figure 1).
Hauksson et al. examine the Mw7.2 El Mayor-Cucapaph mainshock and
aftershock sequence that began on 4 April 2010. They found that the mainshock
was complex and triggered earthquakes to the north along the Elsinore and San
Jacinto faults (Figure 2). The focal mechanisms of the mainshock and M4+
aftershocks exhibit mostly northwest to west- northwest-striking dextral strikeslip
faulting, although the faulting in the Yuha basin is in a region of northwest
and northeast striking faults.
40 | Southern California Earthquake Center
Figure 1. Major earthquake swarms in the
Salton Trough since 1981. Examples of
estimated seismicity migration vectors are
plotted in red. These generally trend SW–
NE at velocities of 0.1 to 0.5 km/hr.