Data Acquisition

Central-site data acquisition for data from the BDSN/NHFN/MPBO networks is performed by two computer systems in the 2195 Hearst Avenue data center (Figure 3.24). These acquisition systems also collect data from the Parkfield-Hollister electromagnetic array and for the BARD network. A third system is used primarily for data exchange with the USNSN and transmits data to the USNSN from HOPS, CMB, SAO, WDC, HUMO, MOD, MCCM, and YBH. Data acquisition for the HRSN follows a more complicated path, as described in Section 3.4.. During the year, we also collected data from USArray travelling array stations deployed in Northern and Central California from the orb-server of the Anza Network Facility at the University of California San Diego.

Figure 3.25: Dataflow in the REDI processing environment, showing waveform data coming in from the Quanterra data loggers (Q) into comserv. From comserv, data are logged to disk (via datalog), distributed to other computers (mserv), fed into the CDA for REDI processing, and spooled into a trace ring for export.

The BSL uses the program comserv developed by Quanterra for central data acquisition. This program receives data from a remote Quanterra data logger, and redistributes the data to one or more comserv client programs. The comserv clients used by REDI include datalog, which writes the data to disk files for archival purposes, cdafill, which writes the data to the shared memory region for REDI analysis, and other programs such as the seismic alarm process, the DAC480 system, and the feed for the Memento Mori Web page (Figure 3.25).

The two computers performing data acquisition also serve as REDI processing systems and hold the databases now used by these systems for storing earthquake information. In order to facilitate REDI processing, each system maintains a shared memory region that contains the most recent 30 minutes of data for each channel used by the REDI analysis system. All REDI analysis routines first attempt to use data in the shared memory region, and will only revert to retrieving data from disk files if the requested data is unavailable in the shared memory region.

Each BDSN datalogger that uses frame relay telemetry is configured to enable data transmission simultaneously to two different computers over two different frame relay T1 circuits to UCB. However, the BSL normally actively enables and uses only one of these data streams from each station at any given time. The comserv client program cs2m receives data from a comserv and multicasts the data over a private ethernet. The program mcast, a modified version of Quanterra's comserv program, receives the multicast data from cs2m, and provides a comserv-like interface to local comserv clients. This allows each REDI system to have a comserv server for every station, and each of the two systems has a complete copy of all waveform data.

We have extended the multicasting approach to handle data received from other networks such as the NCSN and UNR. These data are received by Earthworm data exchange programs, and are then converted to MiniSEED and multicast in the same manner as the BSL data. We use mserv on both REDI computers to receive the multicast data, and handle it in an identical fashion to the BSL MiniSEED data.

In 2006, the BSL established a real-time data feed of all BSL waveforms between the BSL acquisition systems and the NCEDC computers using the open source Freeorb software. This allows the NCEDC to provide near-real-time access to all BSL waveform data through the NCEDC DART (Data Availabile in Real Time) system.

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