Availability of Parkfield data

September 28th, 2004

September 28, 2004

The NCEDC is gathering data related to the 2004 Parkfield earthquake and making them available for researchers. Data are coming in now and will continue to be collected over the next few days and weeks.

Information about the available data is here:

2004 Parkfield earthquake data

The NCEDC is a joint project of the University of California, Berkeley and the USGS. Please send us email at ncedcinfo@ncedc.org or fill out our comments form if you have questions or comments about these changes.

BDSN HH & HL data now continuous

September 25th, 2004

September 25, 2004

As of September 25, the NCEDC is archiving continuous data from the BDSN HH and HL channels. In the past, we had archived waveform snippets or triggers for events for the HH and HL channels, while archiving BH and lower data rates continuously (with a few exceptions such as after large earthquakes such as the Denali and San Simeon events).

With this change in policy, the NCEDC will archive all data transmitted to the BSL. In general, we will not make efforts to fill in missing data from the HH and HL channels, unless the gaps occur in a record of interest. Our usual efforts to provide continuous data for the other channels will be the same.

The NCEDC is a joint project of the University of California, Berkeley and the USGS. Please send us email at ncedcinfo@ncedc.org or fill out our comments form if you have questions or comments about these changes.

BDSN BH channels changed to 40 Hz sampling

June 15th, 2004

June 15, 2004

The BSL converted most - but not quite all - of the BDSN BH data streams from 20 samples per second to 40 samples per second at the beginning of the GMT day on June 15th (day 167). This change affects: BDM, BKS, BRIB (broadband sensor only), CMB, CVS, FARB, HOPS, HUMO, JCC, JRSC, MHC, MNRC, MOD, ORV, PACP, PKD, POTR, RFSB (surface strong-motion only), SAO, SCCB, WDC, and YBH. Stations BRK, KCC, and WENL will be converted at the beginning of day 168.

As a result of this upgrade, stations CMB and SCCB are currently down, but we anticipate that they will be back up shortly.

This change in sampling rate was made in order to be consistent with the USArray specifications. USArray is part of the Earthscope project to study the structure and evolution of the North American continent.

At this time, we do no intend to change the sampling rate of the BP channels associated with the BSL borehole networks - the NHFN, MPBO, and HRSN.

June 16, 2004 - update

We completed the migration of the remaining BDSN stations today - BRK, KCC, and WENL. In addition, both CMB and SCCB have been brought back online.

The NCEDC is a joint project of the University of California, Berkeley and the USGS. Please send us email at ncedcinfo@ncedc.org or fill out our comments form if you have questions or comments about these changes.

Discrepancy in magnitude from database search

June 14th, 2004

June 14, 2004

We have discovered an inconsistency between the magnitudes reported in the new database search of the UC Berkeley earthquake catalogs (http://www.ncedc.org/db/Search/PI/dbselect.html) and the older, flat file search ( http://www.ncedc.org/ncedc/catalog-search.html). The inconsistency arose during the conversion of the catalog from an older PC-based database. The magnitudes currently reported in the database search were computed using a older set of station adjustments and thus differ from the magnitudes reported in the flat file search.

We are currently looking into the best way to resolve this inconsistency. For the present, we advise users for whom magnitude is a critical parameter to use the flat file search.

The NCEDC is a joint project of the University of California, Berkeley and the USGS. Please send us email at ncedcinfo@ncedc.org or fill out our comments form if you have questions or comments about these changes.

Calpine/LBL Geysers data added to the NCEDC

April 3rd, 2004

The NCEDC is pleased to announce the availability of seismic phase and waveform data from the Calpine/Lawrence Berkeley Labs seismic network that monitors seismicity in the vicinity of the Geysers geothermal field. The phase data begins 2003/04/04. Calpine/LBL stations can be recognized with their network code of "BG".

The BG data lowers the magnitude detection threshold for earthquakes at the Geysers and improves the location accuracy. For example, for the month of January, 2003 the NCSN located 248 earthquakes at the Geysers geothermal area. In that same period in 2008 we located 1,014 earthquakes, representing a four-fold increase. The large number of earthquakes that occur at the Geysers exceeds the reviewing capabilities of the NCSN staff. Consequently, only earthquakes above M1.0 at the Geysers are reviewed by analysts. Smaller magnitude events at the Geysers that are automatically detected by the CISN software are also in the catalog, but generally not reviewed.

The dense BG network allows detection of earthquakes at the Geysers with magnitudes lower than 1.0. The algorithm to compute coda durations was not designed for “short” codas (i.e., less than 7 sec). Therefore, earthquakes with magnitudes smaller than 1.0 typically have few, if any coda durations. Consequently, these small events have Md values of zero, which represents “no magnitude”. We anticipate developing a method to compute amplitude magnitudes for earthquakes below M3.0. We will then retroactively apply this method to all historic data. We have no estimated date for completion of this effort.

There is a temporary gap in BG phase data starting 2006/11/29 when the NCSN and UCB networks migrated to CISN processing software. On 2007/07/23 the NCSN established telemetry to the Calpine data acquisition system at the Geysers. This allowed the NCSN to integrate BG data into the CISN system in near real time. We have the BG phase and waveform data for this time gap, but we have no plans to integrate it into the catalog.

We expect event waveform data from the BG network for the period 2003/04/04 – 2006/11/29 to be online by the end of 2009. BG waveform data after 2007/07/23 is available, but as events only. The bandwidth of continuous waveform data recorded by the Calpine/LBL network exceeds the bandwidth of the communications link into the NCSN system. Therefore, continuous BG data is not available at the NCEDC.

The California Integrated Seismic Network greatly appreciates the cooperation of Calpine and Lawrence Berkeley Labs in monitoring earthquakes in California and their willingess to make this data set available to the public.


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