Catalog Generation

The Caltech Seismological Laboratory, the USGS, and the Southern California Earthquake Data Center (SCEDC) have been working toward compiling and converting all available historic seismic data holdings to create a single-source for online access to southern California earthquake data. The SCEDC’s Oracle 9i database now contains all of the supporting data for Southern California earthquakes from 1932-present. *

The earthquake catalog information available at http://www.data.scec.org/catalog_search/ provides a one-line summary of events’ parameters and provides fundamental earthquake information including the event’s date and time, location (latitude, longitude and depth), magnitude and the event’s reference identification number (EVID).
The catalog search has five tabs that allow searching by:

Users interested in accessing the more detailed earthquake information that is used to develop the catalog information e.g., phase-picks, waveforms, station information, etc. can access this data from the Data Center’s STP (Seismic Transfer Program) program. STP is a client-side program for retrieving triggered and continuous waveform and phase data from the Southern California Earthquake Data Center. This program can be run from the Web-based graphical interface at:

http://www.data.scec.org/STP/stp.html

* Data from 1978-1980 is currently unavailable on this search, but can be found at:

http://www.data.scec.org/ftp/catalogs/SCSN/

Catalog Status

Although this work is ongoing, we have made the data available to users of the catalog with the following known issues with the catalog (in chronological order):

1932 - 1976: Early Data

The events from the 1932-1976 era of seismic data are derived from the original hand-written phase cards which originally came from hand measurements on drum records. The data were keyed into electronic CUSP (Caltech-USGS Seismic Processing) format on a VAX system from the phase card solutions by a data entry contractor. Each event was later reviewed and located by a Caltech seismic analyst. Some events were located with "hypoinverse," some with "grope" (a CUSP location program) and some with "simulps." (a 3D location program using S and P times) The data were then imported into the SCEDC Oracle database, to make phase and epicenter data available for direct retrieval by users.

1932 - 1971

Minor checking of the events in this era is still required. Locations and magnitudes may change somewhat, but not significantly.

Some events that were not included in the phase cards (for example, aftershocks that were just listed, without "their own" readings) are currently missing, but we plan to add these events.

Magnitudes for this time period use the most recent known ML calibration and attenuation function.

Note that this time period contains some small events that were excluded, probably with good reason, from the canonical catalog. (Hileman et al. "Seismicity of the Southern California Region").

1972 - 1974

These events were located from a combination of drum readings and develocorder readings.

There are missing events during this time period because we cannot find phase information for very small events (about 80% of them "1.7") in "USGS areas" that were listed in the old catalog. If we cannot recover the phases, we will insert the events with only their catalog information but without the supporting phase and amplitude data to verify the locations and magnitudes.

1975 - 1976

Locations are unlikely to change, but magnitudes may change slightly when recomputed using the newest calibration.

1977 - 1980: The CEDAR Era

A problematic four-year span of CEDAR (Caltech Earthquake Detection and Recording) data from 1977-1980 is currently not available to web searching, but has been converted and is being processed to include magnitude information. The waveform data that was available was read from tape and loaded onto the CUSP VAX system and converted to mSEED format.

Some of the problems we need to resolve before we can make this era of data available are:

The waveforms during this era often have sporadic noise spikes. The waveforms are useful for visual picking, but may present problems for numerical processing.

1980

1980 is currently not searchable. These events happened during a time period when a Real Time data acquisition system was working, but the post-processing system (CUSP) was still under development. The untimed events constitute a "backlog" which was never finished due to data translation problems.

At least some of these events need to be picked and located.

We need to enter Wood-Anderson amplitudes (to get MLs) for those events that have them. Then we need to either enter the previously computed Mcs, or recalibrate and recompute Mc or Md for the other events.

We expect to find time problems and events missing caused by unreadable archive tapes.

Events that are completely missing from the converted CEDAR system will need to have their phase data and parametric data entered in the database from the ASCII catalog and "PINK" cards with matched phase data from the Corbett tapes; however, these events will not have supporting waveforms.

1981 - 1999: The CUSP Era

The parametric data from 1981 to present have been loaded into the Oracle 9i database system and the waveforms for that time period have been converted to mSEED format and are accessible through the STP interface. Quality control verification of 1981-2000 historic parametric and waveform data has progressed using a detailed reverse-chronological examination and verification of magnitudes.

There are a number of events that have zero magnitudes during this era. We are working toward getting magnitudes for these events:

1981 - 1982

The timing and locations for these data are good. We need to insert Wood-Anderson amps to get ML.s, and verify or insert magnitudes for other events.

There are still missing events for these years that were not found on the CUSP system, but were listed in the catalog.

1983

Most of the data is good, but there may still be some .backlog. events that still need to be picked.

Wood-Anderson amplitudes may need to be inserted. Magnitudes may need to be verified or inserted.

1984 - 1999

Good data. We expect that the catalog is complete and all but a few events have reasonable magnitudes.

We are aware of some location problems which require a .starting location. feature in Jiggle to fix.

We are aware that the most of the ML.s were computed with an old calibration and attenuation function.

We now have the capability to check all the magnitudes and improve some of the locations during the intense parts of aftershock sequences. We will do this as we have time.

2000 - present: The TriNet - SCSN/CISN Era

The data archived by the Data Center are now available within a few minutes of the origin time of the earthquake. All the data produced by the real-time monitoring network are placed immediately in the SCEDC Oracle database system, where they are subsequently revised by further analysis. A time delay of a few days used to be the standard for new data to be available at the SCEDC; however, since the inception of the SCSN/CISN (formerly TriNet) system and with changes in the daily operations and daily archiving of the Data Center, new earthquake data are available to the community in near real-time.

2000

During 2000, although CUSP was the authoritative system, the TriNet system was running and would take over as the primary system in 2001. The outcome of both systems running concurrently resulted in four possible types of events. The SCEDC has taken the following steps with each of these event types:

1. Identical Hypocenters - Each system generates a solution, resulting in two event IDs for the same event.
   Solution: took the TriNet event and added CUSP data to create a superset of data for the event. The side effect of this solution is that the CUSP event id for this event no longer exists in the catalog.
2. CUSP, but not TriNet - An event exists only in the CUSP system, but not on the TriNet system.
   Solution: relaxed hypocenter constraints slightly to try to match to a TriNet event. If a match, we proceeded as in step 1; else, the event was converted and loaded into the database.
3. TriNet, but not CUSP - An event exists only in the TriNet system, but not on the CUSP system.
   Solution: relaxed hypocenter constraints slightly to try to match to a CUSP event. If a match, we proceeded as in step 1; else, the event is already in the TriNet database, so it continues to exist.
4. Bogus Events - Early in 2000, TriNet.s triggering algorithm generated a high number of noise events. These were investigated and if they were not true network triggers, they were deleted.

The net effect is that we may have some duplicate events for the year 2000. We are gradually removing these by individual inspection.

2001-2003

There may be minor problems with the synthetic Wood-Anderson amplitudes for the time period 2001 through mid-2003. We will ultimately want to recompute the magnitudes to have a consistent catalog.