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by CSMIP
Click on the link below for the full text:
Introduction
A magnitude 5.0 (ML BRK; moment magnitude 5.0 BRK) earthquake
occurred on December 20, 1994 at 2:27 am (PST), approximately 5
km west of Parkfield. The preliminary hypocenter is located at
35.86°N, 120.50°W with a depth near 6 km (USGS).
Table 1 summarizes the strong-motion data at 10 CSMIP
stations, ranging in epicentral distance from 6 to 39 km. The
locations of these stations and other CSMIP stations in the
Parkfield area are shown on the map in the attached figure. The
records from 7 ground-response stations are included in this
early release.
The largest horizontal and vertical accelerations are 0.43
and 0.21 g, respectively. These accelerations were recorded at
Fault Zone #7 located about 9 km from the epicenter.
Interestingly, three nearby stations (Fault Zone #12, Gold Hill
#1W and Turkey Flat #1) all recorded significantly smaller
accelerations of 0.1 g or less. Recovery of data from the many
other CSMIP stations in the Parkfield area continues.
Maximum accelerations from 3 structures are included in this
early release. Peak structural accelerations of 0.09 and 0.20 g
were recorded on the ground floor and roof of a 1-story woodframe
school building in Parkfield. Peak accelerations of 0.01
and 0.02 g were recorded at the base and roof, respectively of a
1-story hospital in Templeton approximately 39 km SW of the
epicenter. A peak acceleration of 0.05 g was recorded at a small
concrete bridge abutment 24 km south of the epicenter.
Processed acceleration, velocity and displacement and
response spectra (preliminary) from Fault Zone #7, Turkey Flat #1
and the 1-story School Building in Parkfield are included in this
early release. The early processing and release of these data
take advantage of new developments in instrumentation and
communications. Files of the processed data from the 2 ground response
stations can be obtained on the Internet.
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