Welcome to the fourth issue of the Southern California Earthquake Data Center's electronic newsletter. We produce this semiannual compilation of news and information about the SCEDC as part of our continuing efforts to keep users informed about the Data Center and promote the data, tools and services we provide at the SCEDC.
If you would like to subscribe to our mailing list, you can sign up (or unsubscribe) at: http://www.data.scec.org/mailman/listinfo/scedc_users. Please send your questions, comments and suggestions on this newsletter or any SCEDC issues to: vikki_at_gps.caltech.edu.
In This Issue:
A. The Archive
B. What's new with STP (Seismic Transfer Program)?
C. NetDC now Available at the SCEDC
D. XML at the SCEDC
E. Station Information System (SIS) Development
F. User Feedback on the SCEDC
The Archive: By the Numbers
Total size of the waveform archive: 4,575 GB
Size of SCEDC parametric and waveform database: 243,165,388 rows
Data transferred via STP:
Q3: July 1-September 30:
- 3,318,035 waveforms = average of 26,976 waveforms daily
- 342 gigabytes of waveform data = average of 2,785 megabytes bytes daily = 32 kilobytes per second
Q4: October 1-December 31:
- 5,461,804 waveforms = average of 59,367 waveforms daily = 41.2 waveforms per minute!
- 746 gigabytes of waveform data = average of 8,177 megabytes daily = 94 kilobytes per second.
From July 1 - December 31, 2004, the SCEDC archived:
- 8,448 events
- 1,655,039 waveforms
- 130,283 arrivals
- 438,382 amplitudes
|
magnitude |
Number of |
|
0-1 |
2088 |
|
1-2 |
3391 |
|
2-3 |
612 |
|
3-4 |
82 |
|
4-5 |
13 |
|
5-6 |
3 |
|
# of events |
event type |
|
6189 |
le (local event) |
|
336 |
qb (quarry blast) |
|
1516 |
re (regional event) |
|
175 |
sn (sonic blast) |
|
232 |
ts (teleseism) |
|
8,448 |
TOTAL |
Six month summary of requests for catalog information:
|
July |
92,107 |
|
Aug |
74,309 |
|
Sept |
144,489 |
|
Oct |
73,581 |
|
Nov |
44,271 |
|
Dec |
47,607 |
|
Total |
476,364 |
Continuous Archiving of High-Sample Rate Data
The SCEDC continuously archived high sample-rate data (HH_, HL_ (80 sps) and/or EH_, EL_ (100 sps)) for the following significant events:
Fontana Swarm
EVID: 14116972 Mag = 4.4
Origin date/time: 2005/01/06 14:35:28
lat/long 34.1250, -117.4387
channels/time available: HH_, HL_, EH_ / -2.5h, +21.5h
stations archived: All stations within 50km radius of origin
Sumatra-Andaman Island Earthquake
EVID: 10069653 Mw = 9.0
Origin date/time: 2004/12/26 00:58:50
lat/long: 3.307, 95.947
channels/time available: HH_, EH_ / -0.5h, +5.5h
2004 Parkfield Earthquake
EVID: NC.51147892 Mag = 6.0
Origin date/time: 2004/09/28 17:15:24
lat/long: 35.815, -120.374
channels/time available: HH_, HL_, EH_, EL_ / -6h, +12h
Note: This event is considered a northern California event, and the NCEDC event id is: NC.51147892, however the SCEDC also keeps data for this regional event in our catalog under the event ID: 14094992.
Adobe Hills Swarm (east of Mono Lake)
EVID: NC.51146343 Mag = 5.5
Origin date/time: 2004/09/18, 23:02:17
lat/long: 38.009, -118.679
channels/time available: HH_, HL_, EH_, EL / -6h, +12h
stations archived: All stations within 500km radius of origin
Note: This event is considered a northern California event, and the NCEDC event id is: NC.51146343, however the SCEDC also keeps data for this regional event in our catalog under the event ID: 14091792.
More information on this topic is available at http://www.data.scec.org/about/sigeventsshot.html
B. What's new with STP (Seismic Transfer Program)?
XML Output Format Now Available via STP
For more information on this topic see the XML write-up below and the XML homepage at http://www.data.scec.org/xml/
New STP Client - Version 1.4.1 for Macintosh
In response to requests from the user community, we have recently released a STP console client for the Macintosh. This client is virtually identical to the UNIX and Linux versions, but it operates in the Mac environment and allows users to download SCEDC data directly onto their Mac.
To install STP 1.4.1 for Macintosh:
- download www.data.scec.org/ftp/programs/stp/stp.1.4.1.tar
- double-click the file (stp.1.4.1.tar) that you downloaded and it will create a file called stp.1.4.1 Folder
- from a terminal session, cd into the stp.1.4.1 Folder
- type "make mac_stp" to compile.
*Note: this process requires you to have a C-compiler available on your Macintosh. Development kits with such as Xcode Tools 1.5 are available from Apple's Developer Connection site at: http://developer.apple.com/sdk/index.html
Coda Decay Measurements Now Available via STP
We have created a new STP command to retrieve coda measurements for local earthquakes. This type of measurement has been used to look for spatial and temporal variation in scattering Q. The seismic network uses the coda decay to determine coda-magnitude (Mc) estimates for local events. Measurements are available for most local events from 1980 to June 2001.
The coda measurements are made by an L1-norm fit of a straight line in log space to pairs of time-amp windows, where time is in seconds measured from the start of the coda and the amp is the average of the sum of the absolute values of time series sample amps over a window (typically 2-seconds) centered on the time. 'Q' is the slope of the line (exponential decay with increasing time, a negative value, but is traditionally reported as positive value). 'A' is the log of the amplitude at a time 1 second after start of coda measurement (center of the "hypothetical" 1st window).
An example of the output of the coda command is:
STP> coda -e 28504
28504 le 1984/01/06,00:40:38.076 34.0080 -117.2240 12.48 2.56 l 0.5
NET STA CHAN LAT LON DEPTH PH AFIX AFREE QFIX QFREE TAU QUAL t-t0 dist
--- --- ---- ------- --------- ----- -- ----- ----- ----- ----- ----- ---- ----- -----
CI RVR EHZ 33.9935 -117.3755 266.0 . 3.075 2.677 1.800 1.063 0.000 0.0 -38.08 14.04
WR PEC EHZ 33.8920 -117.1613 582.0 . 3.472 3.144 1.800 1.195 0.000 0.0 -38.08 14.12
CI SME EHZ 33.8229 -117.3562 466.0 . 3.495 3.087 1.800 1.178 0.000 0.0 -38.08 23.90
CI GAV EHZ 34.0225 -117.5049 262.0 . 3.126 2.288 1.800 0.580 0.000 0.0 -38.08 25.92
CI DB2 EHZ 33.7352 -117.0629 591.0 . 4.426 4.113 1.800 1.539 0.000 0.0 -38.08 33.75
[...]
The actual output does not have headings. AFREE and QFREE are values obtained with minimum error fit to observed time-amp pairs. AFIX and QFIX are the value for 'A' giving the minimum error with 'Q' fixed to an assigned value of -1.8. TAU is the relative time value at which the predicted/observed average window amp/counts is equivalent to 1.729e-5 cm/s ground motion. t-t0 is the relative time at start of coda measurement, (e.g., the P-arrival time).
-
CAVEATS:
- There are about 350,000 local events that have coda measurements (over 9,000,000 individual coda measurements in all), but not all local events have coda measurements. In particular, since approximately July, 2001, the coda measurements have not been made because coda-magnitude was abandoned in favor of more accurate amplitude-based determinations.
- We are still experimenting with the information and format of the output and may make changes to it in the near future.
C. NetDC now Available at the SCEDC
The SCEDC is now operating an instance of the IRIS interface, NetDC. NetDC is a traditional email-based tool for requesting data, and by implementing it at the SCEDC, we allow connectivity to a broader, international community.
NetDC is a "one-stop shopping" request system that allows a user to request seismological information from multiple data centers through a single email mechanism. Information is delivered to the user through email and/or FTP in a uniform binary or text format.
Users can make 3 different types of requests:
Inventory - what data is available from any of the participating data centers
Responses - detailed station and channel information in RESP format
Waveform - waveform data
Mailing a Request:
A NetDC request to the SCEDC can be emailed to:
netdc@k2.gps.caltech.edu
Alternatively, the request can be emailed to netdc@fdsn.org
More information on this topic is available at http://www.data.scec.org/netdc/
D. XML at the SCEDC
XML, the eXtensible Markup Language has become the standard format for transferring data between computers and organizations because it is a clearly-defined way to structure, describe, and exchange data. The rapid proliferation of XML and the large number of XML parsers that can be freely integrated into applications has made XML a good format option for the Data Center to distribute seismic data.
The most common applications of XML involve the transmission of information for use by different software applications and systems. The SCEDC is putting effort into XML distribution of seismic data because we anticipate tremendous benefits associated with this method of flexible data exchange between distributed systems.
Why use XML for earthquake data?
- The SCSN produces a wide range of earthquake products, solutions and additional data that are archived in the SCEDC database. Without XML, the SCEDC is restricted to HTML, CSV or other character- or space-delimited formats for displaying and distributing the contents of our database. With the freedom of an extensible format, we have the capability to distribute a much wider range of data than we did previously.
- XML allows information filtering, so researchers can use XML filters to parse for elements that are of interest to their research project, and ignore elements that are not. This allows the Data Center to include a wider range of elements and attributes in the earthquake information we distribute than we have in the past.
- XML documents are self-describing and can be validated by a well-documented schema. Station metadata and earthquake event parameters can be described very differently by different organizations, but if the individual elements are well described in an XML schema, the sender and receiver can communicate with a common vocabulary.
The SCEDC XML schema is located at:
http://www.data.scec.org/xml/event.xsd
Documentation of the schema is available at:
http://www.data.scec.org/xml/event
The SCEDC currently provides event and phase data in XML format from the catalog search pages on the Internet, and via the STP client.
Catalog Search
From the SCEDC catalog search pages at: http://www.data.scec.org/catalog_search/ select "XML" from the Search Format drop-down menu. Before you click the "Submit Results" button, you can click the button to either download the results of your query to a file on your computer, or output to the web page (the default option) to display the results in your web browser in XML format.
STP
To output the results of a query in XML, type 'XML' at the STP prompt. To return to normal output, type "NORM" The STP format will output the results of the phase and event command XML into a named file.
More information on this topic is available at: http://www.data.scec.org/xml/
E. Station Information System (SIS) Development
The SCEDC is developing an improved Station Information System (SIS) for the California Integrated Seismic Network (CISN) Southern California Management Center (SCMC). The goal of this project is to develop a simplified database-driven system that can interact with a single database source to enter, update and retrieve station metadata easily and efficiently. The timeline for this project is to have the system functioning as the primary metadata source for the SCMC by September 1, 2005.
Problem Statement: The current methods of keeping track of all station information at the SCMC are not providing the functionality required to meet the needs of all of the users who need complete, accurate station information from a single source.
Scope: The scope of the system is to develop and implement a simplified metadata information system with the following capabilities:
- Provide accurate station/channel information for active stations to the SCSN real-time processing system.
- Provide accurate station/channel information for active and historic stations that have parametric data at the SCEDC e.g., for users retrieving data via STP from the SCEDC.
- Provide all necessary information to generate dataless SEED volumes for active and historic stations that have data at the SCEDC.
- Provide all necessary information to generate COSMOS V0 metadata information.
- Be updated through a graphical interface that is designed to minimize editing mistakes.
- Allow stations to be added to the system with a minimum, but incomplete set of information using predefined defaults that can be easily updated as more information becomes available. This aspect of the system becomes increasingly important with historic data when some aspects of the meta-data are simply not known.
- Facilitate statewide metadata exchange for both real-time processing and provide a common approach to CISN historic station metadata.
The system that will be developed has two fundamental design requirements:
- A well-designed database that is the single source of information, i.e., the authoritative information is what is contained in the database, not in flat-files or any other databases.
- Applications that interact with the data will interact directly with the database, i.e., they will not check information out of the database, manipulate it in another environment, and repopulate the database with the modified information.
More information and documentation on this topic is available at: http://www.data.scec.org/stations/SIS/
F. User Feedback on the SCEDC
Town-Hall Meeting
On September 20th, the SCEDC hosted a town-hall meeting at the SCEC Annual Meeting in Palm Springs, CA. The purpose of this meeting was to bring together Data Center users to discuss ways of improving our service to the SCEC community. The SCEDC is interested in users' feedback and this meeting was held to solicit input from scientific and engineering users to help establish and prioritize our Data Center goals.
The participants of this meeting presented the following issues as high-priority concerns:
- The SCEDC should have the goal of continuously archiving waveforms at 100 samples per second.
- Improved station metadata was requested. Users requested an expanded availability of dataless SEED volumes as well as simplified access to station data such as a master station list for the archive from 1932-present.
- Synthetic seismograms: the SCEDC should archive and distribute synthetic seismograms generated by local researchers. The user community needs a naming convention that will identify the seismogram as a synthetic and identify the generating source of the waveform (i.e., the original researcher and/or generation method).
- Catalog users want access to all types of magnitudes calculated for events, not just the preferred magnitude.
- Archive borehole seismic data from PBO stations.
SCEDC User Survey
The SCEDC prepared a survey to solicit input from the SCEC community at the Annual Meeting in Palm Springs. We received responses from twelve users and some of the feedback is highlighted below.
How often do you use SCEDC services? (10 responses):
daily: 20% monthly: 50% annually: 30%
What data formats do you prefer? (average of 12 responses; 1 highest; 5 lowest)
SAC format 1.6 mSEED 2.0 SEED volumes 1.8 COSMOS V0/V1 format 4.7
Future directions: what innovations are most important to your research? (average of 12 responses; 1 highest; 5 lowest)
Differential time measurements 2.1 Focal mechanisms 2.0 Automatic cross-correlation relocations 1.9 Source spectra 2.0 Path attenuation spectra 2.1 Increased data from buildings/structures 2.4
What is your overall assessment of the SCEDC? (10 responses)
Excellent: 30% Very good: 60% Good: 10% Fair: 0% Poor: 0%
Highlights of comments received:
- Have phase arrivals incorporated in the SAC files.
- Try to unify parametric catalog with NCEDC -- would be very useful for seismicity studies
- SCEDC has a better interface, but IRIS provides SEED format.
- NCEDC has additional metadata e.g., moment tensors linked to data sets
- Need more slide collection of all earthquake phenomenon and damage. If possible, a digital library of scientific publications.
- I'd like focal mechanisms for recent earthquakes made available through the SCEDC -- near real-time focal mechanisms or moment tensors.
- Why not make available teleseismic: time picks, amplitudes, receiver functions, SKS splitting; local earthquake: time picks, amplitudes, S and P waves?
