This report contains a description of the first part
of the Los Angeles Region Seismic Experiment (LARSE).
To date, LARSE has consisted of two experiments:
passive, which took place in fall, 1993 (LARSE93), and active, which took place
in fall, 1994 (LARSE94). The goal of the 1993 experiment was to collect
waveform data from local and distant earthquakes to obtain three-dimensional
images of lower crust and upper mantle structure in Southern California,
particularly under the San Gabriel Mountains and across the San Andreas fault.
During LARSE93, approximately 88 stations were deployed in a 175-km-long,
linear array across the Los Angeles basin, San Gabriel Mountains, and Mojave
Desert northeast of Los Angeles by scientists from the U.S. Geological Survey,
University of California at Los Angeles, California Institute of Technology,
and University of Southern California. Reftek recorders were deployed one km
apart through the San Gabriel Mountains, and two km apart in the Mojave Desert.
This data set has since been complemented by the results of LARSE94 comprising
land refraction and deep-crustal seismic reflection profiles from offshore
airgun and onshore explosion sources. These additional data sets will be
useful in distinguishing crustal structures from adjacent upper mantle
structures. During the four weeks of continuous recording, over 150
teleseismic and over 450 local (ML2.0
and greater) events
were recorded at each site.
Both teleseismic and local sources provided a wide range of raypath azimuths.
The teleseismic events include a number of earthquakes with epicenters in the
Aleutian Island, Kamchatka, Kuril, mid-Atlantic Ridge, Solomon Island, Japan,
Fiji Island, Peru, and Chile regions. The local events include aftershocks of
recent Southern California earthquakes. The final products of data processing
are 1) half-hour files containing the continuous waveform data recorded at each
station for each day of the experiment, 2) 150-second time-windowed waveform
segments containing local, regional, and teleseismic event arrivals, and 3)
one-hour time-windowed waveform segments containing regional and teleseismic
event arrivals. Array instrumentation, recorded events, and data processing
will be described in this report.
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