Statewide Integration

BSL staff are involved in many elements of the statewide integration effort. The Standards Committee, chaired by Doug Neuhauser, continues to define and prioritize projects important to the development and implementation of the statewide earthquake processing system and to establish working groups to address them (see minutes from meetings and conference calls at http://www.cisn.org/standards/meetings.html).

Dual Station Feeds: Early in the existence of CISN, ``dual station feeds" were established for 30 stations (15 in northern California and 15 in southern California) (Figure 3.8). The Northern California Earthquake Management Center (NCEMC) is using data from the Southern California stations to estimate magnitudes on a routine basis. A subset of these stations are being used for the moment tensor inversions, a computation that is sensitive to the background noise level.

Data Exchange: Pick exchange was initiated between the NCEMC and its Southern California counterpart in 2001-2002. The software CISN has developed to produce and exchange the reduced amplitude timeseries has also been completed. Currently, these timeseries are being exchanged at the NCEMC, but not yet statewide. Using a common format, the CISN partners continue to exchange observations of peak ground motion with one another following an event or a trigger. This step increases the robustness of generating products such as ShakeMap, since all CISN partners now exchange data directly with one another. This also improves the quality of ShakeMaps for events on the boundary between northern and southern California, such as the San Simeon earthquake, by allowing all data to be combined in a single map. Finally, this is a necessary step toward the goal of generating statewide ShakeMaps.

The Software Calibration & Standardization: CISN partners are working to standardize the software used for automatic earthquake processing and earthquake review, as well as to calibrate it. Currently, the software implemented in the NCEMC and in Southern California Management Center is very different. During the past year in the NCEMC, we have worked on preparing a version of the Southern California TriNet software software for implementation as CISN Software in the NCEMC.

• Magnitude: Calibrating magnitude estimates has proven to be more difficult than originally anticipated. As described in 2003-2004, evidence indicates that there is a bias between the northern and southern California estimates of local magnitude $M_{L}$. Efforts to understand this issue have been hampered by the lack of a good statewide dataset. Bob Uhrhammer has selected data from 180 earthquakes distributed throughout the state and comprising recordings from 976 horizontal components from the AZ, BK, CI and NC networks (see Research Study 2.13.). In January, we agreed on a $logA_{o}$ function suitable for statewide use. We are currently determining how to define station-specific corrections for $M_{L}$ using differences for each station-component that has been recorded for a given event. The primary advantage of using this differencing method is that the results are independent of a reference station. A final component of the magnitude efforts is the determination of a magnitude reporting hierarchy. For the near future, each region will continue to use its own preferences for magnitude reporting.

• ShakeMap: At present, ShakeMaps are generated on 5 systems within the CISN. Two systems in Pasadena generate ``SoCal" Shakemaps; 2 systems in the Bay area generate ``NoCal" Shakemaps; and 1 system in Sacramento generates ShakeMaps for all of California. The Sacramento system uses QDDS to provide the authoritative event information for northern and southern California.

  The dearth of stations in the near source region of the 2003 San Simeon earthquake raised the issues of how to measure the quality of a ShakeMap and how to quantify the uncertainty. A subset of the Working Group has been working on this issue, based on the work of Hok and Wald (2003). Lin et al (2006) presented progress toward quantifying ShakeMap uncertainty. When the method is validated, we can use this information to determine a grade.

  A second goal of this effort was to improve the robustness of ShakeMap generation and delivery by taking advantage of the fact that ShakeMaps are generated in the Bay Area, Pasadena, and Sacramento. Ongoing fforts in this direction will likely be based on the new USGS ShakeMap webpages at the National Earthquake Information Center.

• Location Codes: The CISN adopted a standard for the use of ``location" codes (part of the Standard for the Exchange of Earthquake Data (SEED) nomenclature to describe a timeseries based on network-station-channel-location) in the late fall of 2003. USGS and UC Berkeley developers have modified the Earthworm software to support the use of location codes. After the transition at USGS Menlo Park away from the CUSP analysis system to Jiggle in late November, 2006, all networks in the CISN implemented location codes in their systems.

• Metadata Exchange: Correct metadata are vital to CISN activities, as they are necessary to insure valid interpretation of data. CISN is working on issues related to their reliable and timely exchange. The CISN Metadata Working Group compiled a list of metadata necessary for data processing and developed a model for their exchange. In this model, each CISN member is responsible for the metadata for its stations and for other stations that enter into CISN processing through it. For example, Menlo Park is responsible for the NSMP, Tremor, and PG&E stations, while Caltech is responsible for the Anza data. At the present time, dataless SEED volumes are used to exchange metadata between the NCEMC and the SCMC. The Metadata Working Group is developing a Station XML format for metadata exchange. This vehicle is expandable, and will probably allow exchange of a more comprehensive set of metadata than dataless SEED volumes, some which may be necessary for other systems, for example in V0 formatted data.

• Standardization: The CISN's focus on standardization of software continues. For example, the BSL and the USGS Menlo Park are adapting the software running at the SCMC for use at the NCEMC and are currently testing its various elements. The adoption of Jiggle in northern California in late November 2007, was the first step in the implementation of the new software. Current efforts are directed toward the implementation and testing of the complete system (see Section 3.8.).