The major progress made during 1997 is that SMDB and EGFL are now fully available over the Internet:
SMDB at http://smdb.crustal.ucsb.edu/;
EGFL at http://egfl.crustal.ucsb.edu/.
These relational databases allow users to search for earthquake data based on earthquake parameters such as magnitude, location, peak ground acceleration, or epicentral distance. Over the past year, these databases gained significant exposure as indicated by the dramatic jump in Web page accesses and data downloads over the last three months, from September to November 1997 (Figure 1). The past year's achievements discussed in more detail below include:
* Four new access methods have been added to the SMDB to facilitate access for all users.
* We provided direct FTP access to the CDMG and USGS strong motion archives to preserve the integrity of data and to ensure a proper credit to the agencies who collected the data.
* Strong motion data from 20 California earthquakes has been added to the SMDB, and the data set now contains 3745 traces.
* The EGFL has been placed on-line, with parameters for over 84,000 traces available.
NEW ACCESS METHODS FOR SMDB.
At the beginning of the project year, the Strong Motion Database was available only through one search method, the custom search page. While the custom search page allowed a complete range of searching and downloading capabilities from the database, this page took some time and effort to use properly. In order to improve the ease of use of the database, additional access methods were added to the database, including two point-and-click access methods and two text-input access methods (Figure 2).
The two point-and-click access methods show summaries of the data available for the earthquakes and for the stations in the database. The summary by earthquake begins with a page giving the earthquake name, the number of stations recording data for that earthquake, and the owners of the stations (e.g. USGS, CSMIP, etc.). Each earthquake is a clickable link, which when selected shows a summary table listing each trace available for that earthquake. This summary table allows the user to download and/or view an image of each trace. A button is also available that displays a map showing earthquake and station locations.
If the user is more interested in a particular station or type of station, a summary by station similar to the summary by earthquake is also available. The summary by station lists all of the stations in the database, the station owner, and the station location. Each station is a link which shows all of the information in the database about that station, such as its latitude, longitude, and site geology. Also shown is a table listing all of the traces that have been recorded at that station and the earthquake these traces came from. Links between the earthquake and station summary pages allow the user to go back and forth in a seamless manner between these two access methods.
The two new text-input access pages include a basic search page and a SQL (Structured Query Language) search page. The basic search page does not have all of the capabilities of the custom search page, but it is easier to use. The basic search page allows input for earthquake name, station location, magnitude, epicentral distance, and peak ground acceleration.
The SQL search page is available for those who might already have some experience with this database query language. This is an advanced page for those who want to take the time to learn the structure of the Strong Motion Database. This search method is also similar to the original version of the SMDB which is available for SUN workstations.
Because of the improvements to the SMDB, the usage of this Web site has jumped dramatically in recent months. Both the number of Web pages accessed and the amount of data that has been downloaded has increased by approximately a factor of ten over the period September to November 1997 (Figure 1). In 1997, there have been more than 26,000 SMDB Web pages accessed, and more than 440 Megabytes of strong motion data has been downloaded from the site. The Web site has been accessed from 71 different countries, including 519 accesses from Mexico, 397 from Sweden, 316 from Canada, 236 from Japan, and 207 accesses from France.
DIRECT FTP ACCESS FOR CSMIP AND USGS DATA.
As requested by these agencies, many of the download links from the SMDB now point directly to the CSMIP and USGS FTP sites, and these data are no longer obtainable directly from the SMDB. This allows CSMIP and the USGS to keep better track of the use of their data and to have ultimate control over data access. Data that is not available at these FTP sites may still be downloaded from the SMDB. At the present time, 37% of the download links from the SMDB point to either the CSMIP or USGS FTP sites.
ADDTITION OF DATA TO THE SMDB.
In the last year, data from 20 California earthquakes were added bringing the total number of earthquakes represented in the database to 119. This includes 3745 accelerograms from 628 stations. The data set is nearly complete for California earthquakes. In the next year we plan to develop a process of quality control so that the data in the database can be verified and made complete. After this validation process, we hope to make the Strong Motion Database a SCEC-certified product.
PLACEMENT OF EGFL ON-LINE.
In addition to the work completed on the Strong Motion Database, in the last year the Empirical Green's Function Library has also been placed on-line. This database provides parameter and download access to more than 84,000 traces from 1500 southern California earthquakes. A search page and station summary page are available.
The database can be searched on station name or number, station location, site geology, event location, depth, magnitude, and date, seismogram amplitude, back azimuth, epicentral distance, and instrument orientation. The subsequent search results provide links for the user to see additional station or earthquake information, to download data, or to view a map showing earthquake and station locations based on the query results.
We presented the results at the annual meeting of the Seismological Society of America:
Tumarkin, A. A., Tumarkin, A. G. and R. J. Archuleta, 1997, SCEC Seismological Databases on the Web: Seismological Research Letters, 68, No. 2, p. 326.
