| nisee |
National Information Service for Earthquake Engineering
University of California, Berkeley |
Response of Regional Seismicity to the Static Stress Change Produced by the Loma Prieta Earthquake.
Paul A. Reasenberg & R. W. Simpson, USGS, Menlo Park, California.
Earthquake data were obtained from the catalog of the Northern
California Seismic Network, U.S. Geological Survey, Menlo Park,
California. For the study area, earthquake hypocenters were
selected for all events between January 1, 1969 and March 31,
1992. These data are archived in the file
lp_seismicity.raw.
Earthquake clusters were identified and removed by a computer
program. The clustering program identified 3296 clusters, which
included 30,457 earthquakes. Each identified cluster was replaced
by a single pseudoevent representing it. The pseudoevent's magnitude
corresponds to the cumulative moment of the cluster, its location
is that of the cluster's centroid, and its origin time is that
of the cluster's largest event. Other details of the cluster
recognition and removal algorithm are described in Reasenberg
(1985). The result of the declustering procedure is archived in
the file
lp_seismicity.dec.
Regional subsets of earthquakes corresponding
to the immediate aftershocks include all earthquakes within 5
km of any of the model fault segments in each zone. These data
are archived in file
Zone1,
Zone2N,
Zone2S,
Zone3,
Zone4 and
Zone5.
+----------------------------------------------------------+
| README file |
| corresponding to the archived seismicity data |
| used in "Response of Regional Seismicity to the Static |
| Stress Change Produced by the Loma Prieta Earthquake" |
| by Paul A. Reasenberg and Robert W. Simpson, |
| Chapter on Postseismic Effects, |
| U.S. Geological Survey Professional Paper |
+----------------------------------------------------------+
1. ABSTRACT
Earthquake data were obtained from the catalog of the Northern California
Seismic Network, U.S. Geological Survey, Menlo Park, California. For the study
area shown in Figures 4 through 8, earthquake hypocenters were selected for all
(M >= 1.0) events between January 1, 1969 and March 31, 1992. These data are
archived in the file lp_seismicity.raw. A subset of this file consisting of M
>= 1.5 events was used to prepare Figures 4, 5, 6 and 8.
Figure 7 was prepared with a data set derived from the raw catalog data.
Earthquake clusters in this file were identified and removed by a computer
program (Program CLUSTER5 was used; see Reasenberg, P., J. Geophys. Res. vol.
90, p. 5479, 1985). The clustering program identified 3296 clusters, which
included 30,457 earthquakes (39% of the raw, M >= 1.0 catalog file). Each
identified cluster was replaced by a single pseudoevent representing it. The
pseudoevent's magnitude corresponds to the cumulative moment of the cluster,
its location is that of the cluster's centroid, and its origin time is that of
the cluster's largest event. Other details of the cluster recognition and
removal algorithm are described in Reasenberg (1985). The result of the
declustering procedure is archived in the file lp_seismicity.dec. Figure 7 was
prepared with a subset of this "declustered" file consisting of M >= 1.5
events.
Figure 12 was prepared with regional subsets of earthquakes corresponding to
the immediate aftershock zone (Zone 1), the northern part of the creeping
section of the San Andreas fault (Zone 2N), the southern part of the creeping
section of the San Andreas fault (Zone 2S), the San Francisco Peninsula (Zone
3), the San Gregorio fault (Zone 4), and the Hayward fault (Zone 5). The
subsets include all earthquakes (M >= 1.5) within 5 km of any of the model
fault segments in each zone (see Table 1). These data are archived in the files
Zone1, Zone2N, Zone2S, Zone3, Zone4 and Zone5.
2. ASCII DATA FORMATS
1. File lp_seismicity.raw is written in Hypoinverse format (F. Klein,
USGS Open-File Report 89-314)
2. File lp_seismicity.dec is written in a modification of
Hypo71 format (W.H.K. Lee and J.C. Lahr, USGS Open-File
Report 75-311), in which columns 1 to 80 are
in hypo71 format, and columns 81 to 90 are appended to these.
In these extra 10 columns, column 87 is "0" for
earthquakes and is blank for "pseudoevents" (see Abstract in
data archive), and column 89 is "+" for earthquakes and "X" for
pseudoevents, where "X" may be any letter. The other extra
columns are blank.
3. Files Zone1, Zone2N, Zone2S, Zone3, Zone4 and Zone5 are written in
Hypo71 format
3. SIZES OF ARCHIVE FILES
Filename Number of Number of
Lines Bytes
lp_seismicity.raw 78666 10462578
lp_seismicity.dec 51165 4656015
zone1 1195 94405
zone2N 2032 160528
zone2S 6105 482295
zone3 615 48585
zone4 166 1311
zone5 796 62884