Abstract
This report describes seismic data obtained during the fourth Seismic
Hazard
Investigation of Puget Sound (SHIPS) experiment, termed Seattle SHIPS
. The
experiment was designed to study the influence of the Seattle sedimentary
basin on
ground shaking during earthquakes. To accomplish this, we deployed seismometers
over
the basin to record local earthquakes, quarry blasts, and teleseisms during
the period of
January 26 to May 27, 2002. We plan to analyze the recordings to compute
spectral
amplitudes at each site, to determine the variability of ground motions
over the basin.
During the Seattle SHIPS experiment, seismometers were deployed at 87
sites in
a 110-km-long east-west line, three north-south lines, and a grid throughout
the Seattle
urban area (Figure 1). At each of these sites, an L-22, 2-Hz velocity
transducer was
installed and connected to a REF TEK Digital Acquisition System (DAS),
both provided
by the Program for Array Seismic Studies of the Continental Lithosphere
(PASSCAL) of
the Incorporated Research Institutes for Seismology (IRIS). The instruments
were
installed on January 26 and 27, and were retrieved gradually between April
18 and May
27. All instruments continuously sampled all three components of motion
(velocity) at a
sample rate of 50 samples/sec. To ensure accurate computations of amplitude,
we
calibrated the geophones in situ to obtain the instrument responses.
In this report, we discuss the acquisition of these data, we describe
the processing
and merging of these data into 1-hour long traces and into windowed events,
we discuss
the geophone calibration process and its results, and we display some
of the earthquake
recordings.
|