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)

NetDC available at the NCEDC

January 23rd, 2000

January 23, 2000

NetDC (Networked Data Centers), a system that allows users to easily and transparently request and retrieve information about seismic and geophysical network data from multiple data centers, is now available at the NCEDC.

A NetDC request is a simple text request file that is emailed to any NetDC data center. NetDC will either email the response back to the user, or place the response in anonymous ftp for the user to retrieve, and notify the user via email with the location of the response. NetDC provides the structure for data centers to communicate requests from users to the appropriate data center that can satisfy the users's request, and will route the response back to the user.

NetDC incorporates all of the BREQ_FAST data request capabilities, and allows user to request other types of information about networks, stations, and channels. A NetDC request can be used to retrieve the following types of information:

Inventory information - list of data centers, list of networked serviced by each data center, list of stations, list of channels, and list of waveforms available within a specified time window.
Instrument response in ASCII format for specified data channels and time windows.
Waveform data for specified network, station, channel, location, and time window.
Data from the BK (Berkeley Digital Seismic Network/Northern Hayward Fault Network/Mini Plate Boundary Observatory Project), BP (High Resolution Seismic Network), and UL (USGS Low-frequency network) networks are available using NetDC at the NCEDC. Work is underway to make the NC (USGS Northern California Seismic Network) data available from NetDC.

NetDC may be used to access data from the NCEDC in two different ways. Users may email their NetDC requests to netdc@ncedc.org or may use the NCEDC waveform request form, which is a web interface for for users to query the NCEDC waveform inventory, create, and submit a NetDC request.

For more information about using NetDC and examples of requests, see the resources below:

NCSN Data Y2K Compliant

October 21st, 1999

October 21, 1999

The traditional formats used for archiving and distributing the NCSN earthquake catalog, phase, and focal mechanism data at the NCEDC were not Y2K compliant, as they contained only a 2 digit years. On October 21, 1999 the NCEDC started distributing the data in an updated Y2K compliant format. You can find documentation on the new Y2K compliant format on our documentation page.

The CNSS and UCB formats for catalog and phase data have not been changed, as they are Y2K compliant.

NCSN Byteorder problem resolved

October 20th, 1999

October 20, 1999

We have corrected the byte order problem that was detected earlier this year in a number of NCSN grm (waveform) files at the NCEDC. See the announcement: Byteorder problem detected in some NCSN waveform files for details.

A few (~ 500) of these events were determined to have possible problems, and will be reloaded from tape in the near future.

BK Network data available in SEED format

October 4th, 1999

October 4, 1999

As of October 4, 1999, the NCEDC can distribute all data for the entire BK network in SEED format with complete multi-stage instrument responses. This includes all seismic channels (broadband and strong motion), electric and magnetic field channels, and other geophysical channels from temperature and microbarograph sensors. The BK network includes the sparse broadband array known as the Berkeley Digital Seismic Network (BDSN) and the borehole sites of the Northern Hayward Fault (and, as of 2002, the borehole sites of the Mini-Plate Boundary Observatory Project).

Prior to this date, only a subeset of the BK network was available in full SEED format, and the instrument responses for the BDSN stations were described by a single-stage response which were not compatible with evalresp.

Most of the BK data channels are acquired from broadband seismic instruments, strong motion seismic instruments, electric field, or magnetic field sensors, and are described using multi-stage responses that are compatible with IRIS's evalresp program. However, selected channels, such as the temperature channel LKS and microbarograph channel LDS do not have responses can be represented with standard poles and zeros used for seismic sensors. These channels are described with a new POLYNOMIAL blockette which is currently not evalresp compatible.

IRIS has released a new version of RDSEED which will properly generated the response files for these channels, which is available from the IRIS DMC.

You may request BK data in SEED format by any of several methods.

  • You may query the BK data inventory at the NCEDC or generate and submit a NETDC request using the SEED Request form
  • You may send a NETDC request to netdc@ncedc.org.

Note: on November 15, 2001, a new tool was added for querying the inventory of SEED data at the NCEDC.

If you have any problems with the new SEED volumes or SEED instrument responses, please contact us at ncedcinfo@ncedc.org.

Contact us: ncedcinfo@ncedc.org
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