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
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
- 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 .
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 function suitable for statewide use. We are
currently determining how to define
station-specific corrections for 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
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
- 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.).
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