Real-time earthquake information during USGS Internet cut-off

December 6th, 2001

Update on Dec. 9, 2001: The USGS Web sites are back!

On Thursday, Dec. 6, 2001, the USGS was ordered to disconnect all external Internet connections by the Office of the Secretary of the Interior. The order includes email as well as popular Web pages.

Because earthquake reporting is a collaborative effort by the CISN members, earthquake information for California continues to be available to emergency responders and the public.

Real-time earthquake information is available at these alternate Web sites:

The "Did you feel it?" Web pages are unavailable at this time.

Access to the Northern and Southern California Earthquake Data Centers and the Engineering Strong-Motion Data Center is unaffected.

EVT_FAST system provides access to NCSN waveform data

November 16th, 2001

November 16, 2001

The USGS Northern California Seismic Network (NCSN) has recorded seismic waveforms for events in northern California from 1984 through present time. These data are archived at the NCEDC, and are now available to users via the EVT_FAST automated event waveform retrieval system through web and email requests. The EVT_FAST system allows users to request all of the waveforms for a specified NCSN event with a simple one-line request. Users can request event waveform data in one of the following formats:

  • SAC binary
  • SAC ascii
  • AH (XDR)

The NCEDC is committed to distributing all waveform data and corresponding instrument response data in the standard SEED format, and is actively working with the USGS to assemble the required instrument response data for the NCSN waveforms. Until the instrument response meta-data is available, the EVT_FAST system provides a quick and easy way for users to acquire NCSN waveform data.

The EVT_FAST web interface for requesting NCSN event waveform data can be found at: /ncedc/evt_fast_form.html

Documentation on the EVT_FAST request format and email submission can be found at: http://www.ncedc.org/ftp/pub/doc/cat5/EVT_FAST.5

The NCEDC is a joint project of the University of California, Berkeley and the USGS. For more information on this data set, please contact ncedcinfo@ncedc.org.

SeismiQuery web interface available

November 15th, 2001

November 15, 2001

The SeismiQuery program, a web-based program developed by the IRIS DMC, is now available the NCEDC. SeismiQuery provides users with a variety of pre-formatted queries concerning waveform data, instrument response, and channel information database from the NCEDC using easy point-and-click or forms-based requests.

Although the name SeismiQuery may imply seismic data, the program provides information about all waveform and related channel information and responses for any data in the NCEDC database. This include broadband and strong motion waveform data from:

  • The UC Berkeley BDSN/NHFN/MPBO (network code BK)
  • The extensive geophysical waveform data from the USGS Low Frequency Geophysical Network (network code UL)
  • (in the near future) the USGS NCSN network (network code NC).

The SeismiQuery program can be found at: /SeismiQuery/

The NCEDC is a joint project of the University of California, Berkeley and the USGS. For more information on this data set, please contact ncedcinfo@ncedc.org.

USGS Low Frequency Geophysical Data available

October 19th, 2001

October 19, 2001

The Northern California Earthquake Data Center (NCEDC) and the U.S. Geological Survey (USGS) are pleased to announce the availablity of extensive "low frequency" geophysical and fault monitoring data.

With National Earthquake Hazards Program (NEHRP) funding, the USGS has supported various fault monitoring efforts. In addition to monitoring at seismic frequency bands, the USGS also has supported strain, creep, water level and other instrumental systems operating at "low frequency". Principal investigators include both USGS and academic scientists. The typical observation interval for these data sets is 10 minutes (0.00167 hz).

Raw data from most of these instruments are now available at the NCEDC, and are archived with the FDSN assigned network code "UL". The "SeismiQuery" web interface, initially developed by IRIS, can be used at the NCEDC to query the inventory and responses for this data. The raw low frequency data can be accessed with seismic querying tools such as NETDC and BREQ_FAST, and NCEDC web forms, and are are retrieved in SEED format, a standard format adopted for seismic data. The NCEDC raw data archive for this network consists of data from 1974 to the present, contains over 800 channels of data, and includes over 354 active data channels that are updated on a daily basis.

In a companion effort, the USGS is providing access to preliminary cleaned versions of these data that have been automatically scaled and modified to remove offsets and telemetry glitches. No checking of these data or the parameters used to generate them is currently being done. Careful review of the data should be done before any scientific conclusions can be drawn. The data do however provide a starting point for general viewing of fault behavior. The cleaned time series are available as plots (most recent week, most recent month, most recent year, and complete time series) and as downloadable files in either a tabular format or as an eXtensible Markup Language (XML) file.

The raw data can be found at: http://www.ncedc.org/ul/

The cleaned data can be found at: http://earthquake.usgs.gov/monitoring/deformation/data/download/

The NCEDC is a joint project of the University of California, Berkeley and the USGS. For more information on this data set, please contact ncedcinfo@ncedc.org.

Quanterra Timing Errors

July 1st, 2000

July 1st, 2000

This description of the Quanterra timing errors is primarily taken from the 1999-2000 Annual Report of the Berkeley Seismological Laboratory.

In late 1998, Quanterra provided the first release of MultiSHEAR, an enhanced version of its data acquisition software that was year 2000 compliant, and updated components of the OS/9 operating system to address the year 2000 problem. MultiSHEAR contained a number of enchancements, especially in the area of multi-site data collection, and introduced a totally new configuration procedure. The BSL worked with Quanterra during 1999 to enhance the configuration procedures to address the diverse needs of the BDSN and NHFN station configurations. During November and December 1999, all of the BSL Quanterra dataloggers were updated to MultiSHEAR with the corresponding OS/9 modifications, which addressed the year 2000 problems.

One significant feature of MultiSHEAR that affected the BSL were the correction of a systematic timing error of the decimated channels from SHEAR and UltraSHEAR software in the Quanterra datalogger.

Quanterra timing correction
The timing description in the following section is provided courtesy of the USGS Albuquerque Seismological Laboratory (ASL), which provides data collection and quality control procedures for the portion of the GSN that uses Quanterra dataloggers.

The Quanterra digitizers initially sample at very high rates. In firmware the data are introduced to a filter cascade of a various number of stages wherethey are low-pass FIR filtered and decimated multiple times. Depending on the specific system the data are further FIR filtered and decimated by configurable software. Each applied FIR filter introduces to the data a nominal delay of half the FIR filter width which then requires subsequent corrections to the data time tags.

For these Quanterra systems the calculation of the time tag applied to the data is more complicated than the first order correction associated with the half widths of the FIR filters. There is a very small correction term associated with data buffering and a more substantive subjective correction to account for the delay in reading the 'first break' during signal onset. This second term attempts to bridge the gap between impulsive and steady state signals. The size of this term has been a function of each filter's transition band and is generally 1.5-2.0 output samples. The cumulative effect of these corrections has mistimed most of the seismic channels. The mistiming is obvious when a sine wave is input into the Quanterra system and time series from the various channels are overplotted.

For more information on this problem from the ASL, please see their Web site on this subject.

These timing errors apply both to the raw data and to the phase readings of the BDSN and NHFN. Neither the raw data nor the phase readings have been corrected. The following tables provide the timing corrections required for the various Quanterra datalogger configurations used by the BSL.






BDSN Qunaterra
Q680, Q980, Q935 dataloggers
Channel Sample Rate Correction
&nbsp (Hz) (seconds)
H?? 80 0.000
B?? 40 0.0025
B?? 20 -0.005
L?? 1.0 -0.688
V?? 0.1 -0.189
Table 1: Time tag correction for Qunaterra Q680, Q980, and 935 systems running SHEAR and UltraSHEAR software. The time correction in the table should be added to the original time series timetags.






BDSN Qunaterra
Q4120 seismic dataloggers
Channel Sample Rate Correction
&nbsp (Hz) (seconds)
H?? 100 -0.00587
B?? 20 +0.03913
L?? 1.0 +1.06413
V?? 0.1 ???
Table 2: Time tag corrections for Quanterra Q4120 seismic systems running UltraSHEAR software. The time corrections in the table should be added to the original timeseries timetags.






BDSN Qunaterra
Q4120 electro-magnetic dataloggers
Channel Sample Rate Correction
&nbsp (Hz) (seconds)
B?? 40 +0.02277
L?? 1.0 +1.08527
Table 3: Time tag corrections for Quanterra Q4120 electro-magnetic systems running UltraSHEAR software. The time corrections in the table should be added to the original timeseries timetags.






BDSN/NHFN Quanterra
Q4120 dataloggers
Channel Sample Rate Correction
(Hz) (seconds)
CL?,DP? 500 -0.00633
HL?,EP? 100 -0.02161
B? 20 +0.02339
L? 1.0 +1.04839
Table 4: Time tag corrections for Quanterra NHFN Q4120 systems running UltraSHEAR software. The time corrections in the table should be added to the original timeseries timetags.

MultiSHEAR Upgrade

The BDSN/NHFN Quanterra dataloggers were upgraded to MultiSHEAR software at the end of 1999. The exact date of the upgrade and the datalogger model are listed in this table. Data recorded after these dates do not have the systematic timing errors.






Quanterra Data Loggers
Date of MultiSHEAR Upgrade
Station Date Data Logger
ARC 1999.346,18:19 Q980
BDM 1999.337,19:26 Q4120 (BDSN)
BKS 1999.338,07:11 Q980
BRIB 1999.309,07:47 Q4120 (NHFN)
BRIB 1999.337,02:00 Q980
BRK 1999.356,02:32 Q680
CMB 1999.346,02:35 Q980
CMSB 1999.307,06:53 Q4120 (NHFN)
CRQB 1999.309,02:00 Q4120 (NHFN)
CVS 1999.349,18:17 Q4120 (BDSN)
FARB 1999.351,01:39 Q4120 (BDSN)
HOPS 1999.349,18:19 Q980
JRSC 1999.351,02:17 Q680
KCC 1999.351,22:28 Q980
MHC 1999.351,03:07 Q980
MIN Closed before upgrade Q980
MOD 1999.289,00:00 Q980
ORV 1999.339,04:56 Q980
PKD 1999.354,21:52 Q980
PKD 1999.354,21:51 Q4120 (EM)
PKD1 1999.355,03:04 Q980
PKD1 1999.355,21:55 Q4120 (EM)
POTR 1999.350,00:58 Q4120 (BDSN)
RFSB 1999.309,02:48 Q4120 (NHFN)
RFSB 1999.309,03:24 Q4120 (NHFN)
SAO 1999.341,22:30 Q980
SAO 1999.341,22:58 Q4120 (EM)
SMCB 1999.309,03:52 Q4120 (NHFN)
STAN Closed before upgrade Q680
WDC 1999.284,00:00 Q980
WENL 1999.350,00:53 Q4120 (BDSN)
YBH 1999.346,18:47 Q980
YBIB 1999.308,23:07 Q4120 (NHFN)


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