Subsections


Northern California Earthquake Data Center



Introduction

The Northern California Earthquake Data Center, a joint project of the Berkeley Seismological Laboratory (BSL) and the U.S. Geological Survey at Menlo Park, serves as an online archive for various types of digital data relating to earthquakes in Central and Northern California. The NCEDC is located at the Berkeley Seismological Laboratory, and has been accessible to users via the Internet since mid-1992.

The primary goal of the NCEDC is to provide a stable and permanent archival and distribution center of digital geophysical data for networks in Northern and Central California. These data include seismic waveforms, electromagnetic data, GPS data, strain, creep, and earthquake parameters. The seismic data comes principally from the Berkeley Digital Seismic Network (BDSN) operated by the Seismological Laboratory, the Northern California Seismic Network (NCSN) operated by the USGS, the Berkeley High Resolution Seismic Network (HRSN) at Parkfield, the EarthScope USArray Transportable Array stations in Northern California, the various Geysers networks, and selected stations from adjacent networks such as the University of Reno, Nevada network and the Southern California Seismic Network (SCSN). GPS data are primarily from the Bay Area Regional Deformation (BARD) GPS network and the USGS/Menlo Park GPS surveys. The collection of NCSN digital waveforms dates from 1984 to the present, the BDSN digital waveforms date from 1987 to the present, and the BARD GPS data date from 1993 to the present. The BDSN includes stations that form the specialized Northern Hayward Fault Network (NHFN) and the MiniPBO (MPBO) borehole seismic and strain stations in the SF Bay Region. Additional seismic and strain data from the EarthScope Plate Boundary Observatory (PBO) and the San Andreas Fault Observatory at Depth (SAFOD) are also archived at the NCEDC.

The NCEDC also provides support for earthquake processing and archiving activities of the Northern California Earthquake Management Center (NCEMC), a component of the California Integrated Seismic Network (CISN). The CISN is the California regional organization of the Advanced National Seismic System (ANSS).

2007-2008 Activities

By its nature, data archiving is an ongoing activity. In 2007-2008, the NCEDC continued to expand its data holdings and enhance access to the data. Projects and activities of particular note include:

BDSN/NHFN/MPBO Seismic Data

Archiving current BDSN (Section 1), NHFN (Section 3), and Mini-PBO (Section 3) (all stations using the network code BK) seismic data is an ongoing task. These data are telemetered from 47 seismic data loggers in real-time to the BSL, where they are written to disk files, used for CISN real-time earthquake processing, and delivered in real-time to the DART (Data Available in Real Time) system on the NCEDC, where they are immediately available to anyone on the Internet. In September 2004, the NCEDC began to archive continuous high frequency data (80 Hz and 100 Hz) from all of the BDSN broadband, strong motion, and strainmeter sensors. Previously, 20 Hz and lower rate data channels were archived continuously, and high frequency data was archived only for events. In early 2006, the NCEDC started to receive all of the BK stations in real-time and make them available to users through the DART. All timeseries data from the Berkeley networks continue to be processed and archived by an NCEDC analyst using calqc in order to provide the highest quality and most complete data stream to the NCEDC.

NCSN Seismic Data

NCSN continuous waveform data are sent in real-time to the NCEDC via the internet, and are made available to users in real-time through the NCEDC DART. NCSN event waveform data, as well as data from all other real-time BSL and collaborating networks, are automatically collected by the NCEMC waveform archiver and stored at the NCEDC for event review and analysis and for distribution to users. All NCSN and NCEMC data are archived in MiniSEED format.

The NCEDC also maintains a list of historic teleseismic events recorded by the NCSN, since these events do not appear in the NCSN catalog.

A description of the successive improvements in the acquisition of NCSN data, leading to the acquisition of complete NCSN waveform data in early 2006, can be found in the 2005-06 BSL Annual Report. We have made significant progress this year in the NCSN continuous waveform archiving project by reading, converting and archiving NCSN seismograms from all NCSN tapes for 2003 through early 2006. Figure 3.23 shows the total data volume by year.

Parkfield High Resolution Seismic Network Data

The history of upgrades to the acquisition and archival of HRSN data can be found in the 2005-06 BSL Annual Report.

In early 2006, the NCEDC started to receive the HRSN 20 Hz data and a subset of the 250 Hz data in real-time for distribution through the DART. The NCEDC continued to archive continuous 250 Hz and 20 Hz data streams from the HRSN tapes written in Parkfield and processed at the NCEDC. In early 2007, the BSL established a radio telemetry link from the HRSN recording center at the California Department of Forestry (CDF) in Parkfield to Carr Hill, and started to telemeter all HRSN continuously to UCB. These data are fed into the NCSN backup Earthworm system at Carr Hill, and are also routed through the USGS Parkfield T1 circuit to USGS/MP and through the NCEMC T1 circuit to the BSL for real-time processing by the NCEMC earthquake processing system. The data are also made available to users through the NCEDC DART and are continuously archived at the NCEDC.

EarthScope USArray Transportable Array

EarthScope began installing broadband stations for the Transportable Array component of USArray in California in 2005. The NCEDC started acquiring telemetered continuous data from the Northern California and surrounding stations as they were installed, and is archiving these data to support users working with Northern California seismic data. These data are made available to users using the same data request methods as all other continuous data waveform data at the NCEDC. The Transportable Array stations have a limited operational timespan of 18 to 24 months, after which they will be relocated to new sites across the country. Data from these stations were delivered to the NCEDC as they were received by the BSL for distribution through the DART. The USArray station feed to the BSL was discontinued in late November 2007 when the stations were relocated to new sites outside of California.

EarthScope Plate Boundary Observatory (PBO) strain data

The NCEDC is one of two funded archives for PBO EarthScope borehole and laser strain data. Strain data are collected from all of the PBO strain sites and are processed by UNAVCO. MiniSEED data are delivered to the NCEDC using SeedLink, and raw and XML processed data are delivered to the NCEDC using Unidata's Local Data Manager (LDM). The MiniSEED data are inserted into the NCEDC DART and are subsequently archived from the DART. UNAVCO provides EarthScope funding to the NCEDC to help cover the processing, archiving, and distribution costs for these data.

EarthScope SAFOD

The NCEDC is an archive center for the SAFOD event data and will also process the continuous SAFOD data. Starting in July 2002, scientists from Duke University successfully installed a three component 32 level downhole-seismic array in the pilot hole at the EarthScope SAFOD site in collaboration with Steve Hickman (USGS), Mark Zoback (Stanford University), and the Oyo Geospace Engineering Resources International (GERI) Corporation. High frequency event recordings from this array have been provided by Duke University for archiving at the NCEDC. We converted data from the original SEG-2 format data files to MiniSEED, and have developed the SEED instrument responses for this data set. Continuous 4 KHz data from SAFOD are written to tape at SAFOD and are periodically sent to the BSL to be converted, archived, and forwarded to the IRIS DMC. SAFOD EarthScope funding to the NCEDC is to cover the processing, archiving, and distribution costs for these data. A small subset of the continuous SAFOD data channels are also incorporated into the NCSN, are available in real-time from the NCEDC DART, are archived at the NCEDC, and are forwarded to the IRIS DMC. In March 2008, SAFOD installed a Guralp broadband and accelerometer package in the Pilot Hole, which sends continuous data at 200 samples-per-second to the NCEDC.

Figure 3.21: Map showing the location of stations whose data are archived at the NCEDC. Circles are seismic sites, squares are GPS sites, and diamonds are the locations of USGS low-frequency experiments.
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Table 3.13: Volume of Data Archived at the NCEDC by network
Data Type GBytes
BDSN/NHFN/MPBO (broadband, electric and magnetic field, strain) waveforms 5,026
NCSN seismograms 16,365
Parkfield HRSN seismograms 2,387
BARD GPS (RINEX and raw data) 1,704
UNR Nevada seismograms 880
SCSN seismograms 1,348
Calpine/Unocal Geysers region seismograms 38
EarthScope SAFOD seismograms 972
EarthScope USArray seismograms 271
EarthScope PBO strain waveforms 455
USGS low frequency geophysical waveforms 2
Misc data 114
Total size of archived data 29,562


Figure 3.22: Chart showing the relative proportion of each data set at the NCEDC. (BK - Berkeley Digital Seismic Network; BP - Berkeley High-resolution Seismic Network in Parkfield; NC - Northern California Seismic Network and collaborators; CI - Southern California Seismic Network; NN - University of Nevada, Reno Seismic Network; GPS - various GPS datasets, including BARD; EarthScope - data from various EarthScope activities; Other - various small data sets
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Figure 3.23: Figure showing the total volume of data archived at the NCEDC, broken down by data year.
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UNR Broadband data

The University of Reno in Nevada (UNR) operates several broadband stations in western Nevada and eastern California that are important for Northern California earthquake processing and analysis. Starting in August 2000, the NCEDC has been receiving and archiving continuous broadband data from four UNR stations. The data are transmitted in real-time from UNR to UC Berkeley, where they are made available for CISN real-time earthquake processing and for archiving. Initially, some of the stations were sampled at 20 Hz, but all stations are now sampled and archived continuously at 100 Hz.

The NCEDC installed Simple Wave Server (SWS) software at UNR, which provides an interface to UNR's recent collection of waveforms. The SWS is used by the NCEDC to retrieve waveforms from UNR that were missing at the NCEDC due to real-time telemetry outages between UNR and UC Berkeley.

In early 2006, the NCEDC started to archive continuous data from the UNR short-period stations that are contributed to the NCSN. Both the broadband and short-period UNR stations contributed to the CISN are available in real-time through the NCEDC DART.

Electro-Magnetic Data

The NCEDC continues to archive and process electric and magnetic field data acquired at several UC Berkeley sites. The BSL operates both magnetic and electric field sensors at PKD and SAO. Through a collaboration with Dr. Simon Klemperer at Standord University, we acquire magnetic and electric field channels at BSL sites JRSC and BRIB, and magnetic field channels at site MHDL. The three magnetic field channels and either two or four electric field channels are digitized at 40 Hz, 1 Hz, and 0.1 Hz, and are telemetered in real-time along with seismic data to the Berkeley Seismological Laboratory, where they are processed and archived at the NCEDC in a similar fashion to the seismic data.

Using programs developed by Dr. Martin Fullerkrug at the Stanford University STAR Laboratory (now at the University of Bath), the NCEDC has computed and archived magnetic activity and Schumann resonance analysis using the 40 Hz data from this dataset. The magnetic activity and Schumann resonance data can be accessed from the Web. This processing was halted in mid 2005 due to problems with the code and will be resumed when the problems have been identified and corrected.

The NCEDC also archives data from a low-frequency, long-baseline electric field project operated by Dr. Steve Park of UC Riverside at site PKD2. These data are acquired and archived in an identical manner to the other electric field data at the NCEDC.

GPS Data

The NCEDC continues to archive GPS data through the BARD (Bay Area Regional Deformation) network of continuously monitored GPS receivers in Northern California (Section 5). The NCEDC GPS archive now includes 67 continuous sites in Northern California. There are approximately 50 core BARD sites owned and operated by UC Berkeley, USGS (Menlo Park and Cascade Volcano Observatory), LLNL, UC Davis, UC Santa Cruz, Trimble Navigation, and Stanford. Data are also archived from sites operated by other agencies including East Bay Municipal Utilities District, the City of Modesto, the National Geodetic Survey, and the Jet Propulsion Laboratory.

In addition to the standard 15 second or 30 second continuous GPS datastream, the NCEDC is now privately archiving high-rate 1 Hz continuous GPS data from the 14 stations in Parkfield and from 10 BARD stations. The high-rate Parkfield data are collected by UNAVCO as part of the PBO Nucleus. The Parkfield data are available via anonymous FTP from the NCEDC but are currently not included in the GPS Seamless Archive (GSAC), since the GSAC does not currently handle both high-rate and low-rate data from the same site and day.

The NCEDC continues to archive non-continuous survey GPS data. The initial dataset archived is the survey GPS data collected by the USGS Menlo Park for Northern California and other locations. The NCEDC is the principal archive for this dataset. Significant quality control efforts were implemented by the NCEDC to ensure that the raw data, scanned site log sheets, and RINEX data are archived for each survey. All of the USGS MP GPS data have been transferred to the NCEDC, and virtually all of the data from 1992 to the present has been archived and is available for distribution.

Geysers Seismic Data

The Calpine Corporation operated a micro-seismic monitoring network in the Geysers region of Northern California. Prior to 1999 this network was operated by Unocal. Through various agreements, both Unocal and Calpine have released triggered event waveform data from 1989 through 2000 along with preliminary event catalogs for the same time period for archiving and distribution through the NCEDC. This dataset represents over 296,000 events that were recorded by Calpine/Unocal Geysers network and are available via research accounts at the NCEDC.

The Lawrence Berkeley Laboratory (LBL), with funding from the California Energy Commission, currently operates a 22 station network in the Geysers region with an emphasis on monitoring seismicity related to well water injection. The earthquake locations and waveforms from this network are sent to the NCEDC, and the locations are forwarded to the NCSN so that they can be merged into the NCSN earthquake catalog. In August 2007, the NCSN installed an Earthworm system at the Geysers to receive continuous LBL Geysers data, and this system provides event waveforms in real-time for the NCEMC earthquake procssing and the NCEDC event archives. The event data from LBL Geysers event waveforms collected from April 2004 to August 2007 will be associated with events from the NCSN catalog and will be included with the existing waveforms for these events.

USGS Low Frequency Data

Over the last 30 years, the USGS at Menlo Park, in collaboration with other principal investigators, has collected an extensive low-frequency geophysical data set that contains over 1300 channels of tilt, tensor strain, dilatational strain, creep, magnetic field, and water level as well as auxiliary channels such as temperature, pore pressure, rain and snow accumulation, and wind speed. In collaboration with the USGS, we assembled the requisite information for the hardware representation of the stations and the instrument responses for many channels of this diverse dataset, and developed the required programs to populate and update the hardware database and generate the instrument responses. We developed the programs and procedures to automate the process of importing the raw waveform data and converting it to MiniSEED format. Since these data are delivered to the NCEDC on a daily basis and immediately archived, these data are not inserted into the NCEDC DART.

We have currently archived timeseries data from 887 data channels from 167 sites, and have instrument response information for 542 channels at 139 sites. The waveform archive is updated on a daily basis with data from 350 currently operating data channels. We will augment the raw data archive as additional instrument response information is assembled by the USGS for the channels and will work with the USGS to clearly define the attributes of the ``processed'' data channels.

SCSN/Statewide seismic data

In 2004, the NCEDC started to archive broadband and strong motion data from 15 SCSN (network CI) stations that are telemetered to the Northern California Management Center (NCEMC) of the California Integrated Seismic Network (CISN). These data are used in the prototype real-time state-wide earthquake processing system and also provide increased coverage for Northern California events. Since the data are telemetered directly from the stations in real-time to both the SCSN and to the NCEMC, the NCEDC archives the NCEMC's copy of the data to ensure that at least one copy of the data will be preserved.

In early 2006, the NCEDC started to continuously archive all of the selected SCSN short-period stations that are contributed to the NCSN. All of these data are available in real-time from the NCEDC DART.

Earthquake Catalogs

Northern California: The NCEDC provides searchable access to both the USGS and BSL earthquake catalogs for Northern and Central California. The ``official'' UC Berkeley earthquake catalog begins in 1910 and runs through 2003, and the ``official'' USGS catalog begins in 1966. Both of these catalogs are archived and available through the NCEDC, but the existence of 2 catalogs has caused confusion among both researchers and the public.

In late 2006, the NCEMC begun to archive and distribute a single unified Northern California earthquake catalog in real-time to the NCEDC through database replication from the NCEMC's real-time systems. The NCEDC developed and tested the required programs used to enter all previous NCSN catalog data into the NCEDC database. In 2008, we migrated all of the historic NCSN catalog, phase, and amplitude data from 1967 - 2006 into the NCEMC catalog. In addition, we spent considerable effort addressing the mapping of phase data in the BSL catalog to SEED channel names. We plan to merge the BSL catalog with the NCEMC catalog to form a single unified Northern California catalog from 1910 to the present. The BSL and the USGS have spent considerable effort over the past years to define procedures for merging the data from the two catalogs into a single Northern and Central California earthquake catalog in order to present a unified view of Northern California seismicity. The differences in time period, variations in data availability, and mismatches in regions of coverage all complicate the task.

Worldwide: The NCEDC, in conjunction with the Council of the National Seismic System (CNSS), produced and distributed a world-wide composite catalog of earthquakes based on the catalogs of the national and various U.S. regional networks for several years. Each network updates their earthquake catalog on a daily basis at the NCEDC, and the NCEDC constructs a composite world-wide earthquake catalog by combining the data, removing duplicate entries that may occur from multiple networks recording an event, and giving priority to the data from each network's authoritative region. The catalog, which includes data from 14 regional and national networks, is searchable using a Web interface at the NCEDC. The catalog is also freely available to anyone via ftp over the Internet.

With the demise of the CNSS and the development of the Advanced National Seismic System (ANSS), the NCEDC was asked to update its Web pages to present the composite catalog as a product of the ANSS. This conversion was completed in the fall of 2002. We continue to create, house, distribute, and provide a searchable web interface to the ANSS composite catalog, and to aid the regional networks in submitting data to the catalog.

NCEDC Operations

In 2005, the NCEDC relocated its archive and distribution system from McCone Hall to a new state-of-the-art computer facility in a new seismically braced building on the Berkeley campus. The facility provides seismically braced equipment racks, gigabit ethernet network, air conditioning, and power conditioning. The entire facility is powered by a UPS with generator backup.

The currently installed NCEDC facilities consist of a mass storage environment hosted by a Sun V240 host computer, a 100 slot LTO-2 tape library with two tape drives and a 20 TByte capacity, and 50 TBytes of RAID storage, all managed with the SAM-FS hierarchical storage management (HSM) software. A Sun system provides Web services and research account access to the NCEDC, a dual Sun 280R processor provides data import and export services, and a Sun V20Z computer is used for quality control procedures. Two AIT tape libraries are used to read NCSN continuous data tapes. A 64-bit Linux system hosts a database dedicated to providing data to external users. Two Sun Opteron processors provide additional data processing support for the NCEDC.

The hardware and software system is configured to automatically create multiple copies of each timeseries file. The NCEDC creates one copy of each file on an online RAID, a second copy on LTO2 tape which is stored online in the tape library, and a third copy on LTO2 tape which is stored offline and offsite. All NCEDC data are online and rapidly accessible by users.

The NCEDC operates two instances of its Oracle database, one for internal operations and one for external use for user data queries and data distribution programs. The databases are synchronized using multi-master replication.

Data Quality Control

The NCEDC developed a GUI-based state-driven system calqc to facilitate the quality control processing that is applied to the continuously archived data sets at the NCEDC.

The quality control procedures for these datasets include the following tasks:

Calqc uses previously developed programs to perform each function, but it provides a graphical point-and-click interface to automate these procedures, and to provide the analyst with a record of when each process was started, whether it executed correctly, and whether the analyst has indicated that a step has been completed. Calqc is used to process all data from the BDSN network, and all continuous broadband data from the NCSN, UNR, SCSN, and HRSN networks that are archived by the NCEDC. The remainder of the continuously archived data are automatically archived without any analyst interaction.

The NCEDC is developing programs and procedures to replace waveforms collected for event analysis in near real-time with QC-ed waveforms from the UCB QC-ed waveform archive. This procedure will also be used to augment the NCSN event-based waveform collection from 1991 - 2006 with the appropriate waveforms from the UCB seismic networks.

Database Development

The NCEDC parametric database schema for storing earthquake event information was adopted by the CISN for use within the Northern and Southern California earthquake processing centers as well as the NCEDC and SCEDC. Through the efforts of the CISN Standards Group, this schema continues to be enhanced to address new requirements of the CISN.

The most significant database development this year has been the migration of the entire NCSN earthquake catalog, phase data, and amplitude readings into the NCEDC database. In collaboration with the NCSN, we developed the programs and procedures necessary to migrate the 1967-2006 NCSN catalog into the CISN parametric schema and have been performing quality control procedures on the data prior to entering the catalog into the database. In support of this project, the NCEDC developed the dbselect program which can search the database, retrieve earthquake information, and optionally recreate full Hypoinverse files. The dbselect program is now used in the NCEDC web-based catalog search interface.

The NCEDC continues to support the Northern California Earthquake Management Center (NCEMC) by providing information and resources vital to the NCEMC's role of rapid earthquake analysis and data dissemination. The NCEDC receives earthquake parametric data in real-time from the NCEMC real-time systems and provides real-time access to the NCEDC database for jiggle, the CISN event analysis tool. The NCEMC continues to support the maintenance and distribution of the hardware configurations and instrument responses of the UCB, USGS/MP NCSN, and other seismic stations used by the NCEMC. During 2002-2004, the NCEDC and NCSN jointly developed a system consisting of an extensive spreadsheet containing per-channel information that describes the hardware of each NCSN data channel and provides each channel with a SEED-compliant channel name. This spreadsheet, combined with a limited number of files that describe the central-site analog digitizer, FIR decimation filters, and general characteristics of digital acquisition systems, allows the NCSN to assemble its station history in a format that the NCEDC can use to populate the hardware tracking and instrument response database tables for the NCSN.

The NCEDC instrument response schema represents full multi-stage instrument responses (including filter coefficients) for the broadband data loggers. The hardware tracking schema represents the interconnection of instruments, amplifiers, filters, and data loggers over time, and is used to describe all of the UC Berkeley and USGS stations and channels archived at the NCEDC.

The NCEDC has developed XML import and export procedures to provide better maintenance of the hardware tracking information and resulting instrument responses for stations in our database. When changes are made to either existing hardware or to station configurations, we export the current view in XML format, use a GUI-based XML editor to easily update the information, and import the changes back into the database. When adding new stations or hardware, we can easily use information from existing hardware or stations as templates for the new information. This allows us to treat the database as the authoritative source of information, and to use off-the-shelf tools such as the XML editor and XML differencing programs as part of our database maintenance procedures.

All NCSN event waveforms originally collected with the USGS CUSP processing system have been converted to MiniSEED, and are available along with the UC Berkeley data and data from the other networks archived at the NCEDC in full SEED format.

Additional details on the joint catalog effort and database schema development may be found at http://www.ncedc.org/db

Data Distribution

The NCEDC continues to use the World Wide Web as a principal interface for users to request, search for, and receive data from the NCEDC. In fall 2005, the NCEDC acquired the domain name ncedc.org. The NCEDC's Web address is now http://www.ncedc.org/

Earthquake Catalogs

The NCEDC provides users with searchable access to Northern California earthquake catalogs and to the ANSS world-wide catalog via the web. Users can search the catalogs by time, magnitude, and geographic region, and can retrieve either hypocenter and magnitude information or a full set of earthquake parameters including phase readings, amplitudes, and codas. Moment tensor results are now being added to the NCEMC California earthquake catalog.

Station Metadata

In addition to the metadata returned through the various data request methods, the NCECD provides dataless SEED volumes and SEED RESP files for all data channels archived at the NCEDC. The NCEDC currently has full SEED instrument responses for 12,989 data channels from 1,909 stations in 20 networks. This includes stations from the California Geological Survey (CGS) strong motion network that will contribute seismic waveform data for significant earthquakes to the NCEDC and SCEDC.

SeismiQuery

We have ported and installed the IRIS SeismiQuery program at the NCEDC, which provides a common interface to query network, station, and channel attributes and query the availability of archived timeseries data. We have provided both IRIS and the SCEC Data Center with our modified version of SeismiQuery.

DART (Data Available in Real Time)

The DART (Data Available in Real Time) represents the first step in NCEDC's effort to make current and recent timeseries data from all networks, stations, and channels available to users in real-time. The NCEDC developed DART in December 2005 to provide a mechanism for users to obtain access to real-time data from the NCEDC. All real-time timeseries data streams delivered to the NCEDC are placed in MiniSEED files in a Web-accessible directory structure. The DART waveforms can be accessed by Web browsers or http command-line programs such as wget, a FISSURES waveform server, and a Berkelely-developed Simple Wave Server (SWS) which provides programmatic access to the DART data by specified SEED channel and time interval. We will be providing users with a client program to retrieve data from the SWS in the near future. The DART currently provide assess to the most recent 30 days of data.

We are using the Freeorb software, an enhanced version of the open-source orb software developed by the IRIS-funded Joint Seismic Project (JSP), as the primary method for delivering real-time data to the NCEDC and into the DART. The freeorb package implements an object ring buffer (ORB) and orbserver, which provides a reliable storage ring buffer and an interface for orb client programs to read, write, and query the orbserver. Orbserver clients running at the NCEDC computer connect to remote orbservers at the BSL and USGS/Menlo Park, retrieve the MiniSEED timeseries data records, and write them to daily channel files in the NCEDC DART. Strain data from the EarthScope PBO network are delivered to the NCEDC using SeedLink and are inserted into the DART using a similar SeedLink client program.

The NCEDC developed an automated data archiving system to archive data from the DART on a daily basis. It allows us to specify which stations should be automatically archived, and which stations should be handled by the NCEDC's Quality Control program calqc, which allows an analyst to review the waveforms, retrieve missing data from stations or waveservers that may have late-arriving, out-of-order data, and perform timing corrections on the waveform data. The majority of data channels are currently archived automatically from the DART.

NetDC

In a collaborative project with the IRIS DMC and other worldwide datacenters, the NCEDC helped develop and implement NetDC, a protocol which will provide a seamless user interface to multiple datacenters for geophysical network and station inventory, instrument responses, and data retrieval requests. The NetDC builds upon the foundation and concepts of the IRIS BREQ_FAST data request system. The NetDC system was put into production in January 2000 and is currently operational at several datacenters worldwide, including NCEDC, IRIS DMC, ORFEUS, Geoscope, and SCEDC. The NetDC system receives user requests via email, automatically routes the appropriate portion of the requests to the appropriate datacenter, optionally aggregates the responses from the various datacenters, and delivers the data (or ftp pointers to the data) to the users via email.

STP

In 2002, the NCEDC wrote a collaborative proposal with the SCEDC to the Southern California Earthquake Center, with the goal of unifying data access between the two data centers. As part of this project, the NCEDC and SCEDC are working to support a common set of 3 tools for accessing waveform and parametric data: SeismiQuery, NetDC, and STP.

The Seismogram Transfer Program or STP is a simple client-server program, developed at the SCEDC. Access to STP is either through a simple direct interface that is available for Sun or Linux platforms, or through a GUI Web interface. With the direct interface, the data are placed directly on a user's computer in several possible formats, with the byte-swap conversion performed automatically. With the Web interface, the selected and converted data are retrieved with a single ftp command. The STP interface also allows rapid access to parametric data such as hypocenters and phases.

The NCEDC has continued work on STP, working with the SCEDC on extensions and needed additions. We added support for the full SEED channel name (Station, Network, Channel, and Location), and are now able to return event-associated waveforms from the NCSN waveform archive.

EVT_FAST

In order to provide Web access to the NCSN waveform before the SEED conversion and instrument response for the NCSN has been completed, the NCEDC implemented EVT_FAST, an interim email-based waveform request system similar to the BREQ_FAST email request system. Users email EVT_FAST requests to the NCEDC and request NCSN waveform data based on the NCSN event ID. Initially, the NCSN waveform data was converted to either SAC ASCII, SAC binary, or AH format, and placed in the anonymous ftp directory for retrieval by the users. EVT_FAST event waveforms can now also be provided in MiniSEED format and are now named with their SEED channel names.

FISSURES

The FISSURES project developed from an initiative by IRIS to improve earth scientists' efficiency by developing a unified environment that can provide interactive or programmatic access to waveform data and the corresponding metadata for instrument response, as well as station and channel inventory information. FISSURES was developed using CORBA (Common Object Request Broker Architecture) as the architecture to implement a system-independent method for the exchange of this binary data. The IRIS DMC developed a series of services, referred to as the Data Handling Interface (DHI), using the FISSURES architecture to provide waveform and metadata from the IRIS DMC.

The NCEDC has implemented the FISSURES Data Handling Interface (DHI) services at the NCEDC, which involves interfacing the DHI servers with the NCEDC database schema. These services interact with the NCEDC database and data storage system and can deliver NCEDC channel metadata as well as waveforms using the FISSURES interfaces. We have separate FISSURES DHI waveform servers to serve archived and DART data streams. Our FISSURES servers are registed with the IRIS FISSURES naming services, which ensures that all FISSURES users have transparent access to data from the NCEDC.

GSAC

Since 1997, the NCEDC has collaborated with UNAVCO and other members of the GPS community on the development of the GPS Seamless Archive Centers (GSAC) project. This project allows a user to access the most current version of GPS data and metadata from distributed archive locations. The NCEDC is participating at several levels in the GSAC project: as a primary provider of data collected from core BARD stations and USGS MP surveys, and as a wholesale collection point for other data collected in Northern California. We helped to define database schema and file formats for the GSAC project and have produced complete and incremental monumentation and data holdings files describing the data sets that are produced by the BARD project or archived at the NCEDC so that other members of the GSAC community can provide up-to-date information about our holdings. Currently, the NCEDC is the primary provider for over 138,000 data files from over 1400 continuous and survey-mode monuments. The data holdings records for these data have been incorporated into the GSAC retailer system, which became publicly available in late 2002.

In addition, the NCEDC is archiving and distributing high-rate 1 Hz GPS data from 10 BARD stations in addition to the normally sampled 15 second or 30 second data. These high-rate data are now publicly available to the entire community.

Acknowledgements

The NCEDC is a joint project of the BSL and the USGS Menlo Park and is funded primarily by the BSL and the USGS Cooperative Agreement 07HQAG0013. Additional funding for the processing and archiving of the EarthScope PBO and SAFOD data were proviced by EarthScope subawards EAR0350025-06 through UNAVCO and 18036080-28436-F through Stanford University.

Doug Neuhauser is the manager of the NCEDC. Stephane Zuzlewski, Rick McKenzie, Mario Aranha, Nicolas Houlie, Bob Uhrhammer, Jennifer Taggart,and Peggy Hellweg of the BSL and David Oppenheimer, Hal Macbeth, Lynn Dietz, and Fred Klein of the USGS Menlo Park contribute to the operation of the NCEDC. Doug Neuhauser and Peggy Hellweg contributed to the preparation of this section.

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