January - March 1999

Table of Contents

Seismologist/Developer Employed
Royal Society Supplement
ISC and IUGG99
Writing a Program to Retrieve ISC Data
Database Loading Underway
Regional Thresholds
Annual Report

Seismologist/Developer Employed


Thanks to supplementary funding from the US National Science Foundation, the ISC has been able to employ an additional seismologist to help modernise ISC applications. Noureddine Beghoul joined the ISC in January. Following a B.Sc. at the Algiers University, Noureddine earned doctoral degrees in geophysics at the University of Paris and Cornell University. His previous work includes tomographic inversions using regional phase arrival times from the ISC Bulletin. For his first ISC project, Noureddine is working with Dmitry Storchak and Ray Willemann to improve automatic association. Automatic processing correctly associates better than 90% of all readings, but with an average of 30 associated readings, most earthquakes include several association errors. ISC seismologists re-associate thousands of readings each month to produce an accurate Bulletin. An important element of producing a better initial set of associations will be using preliminary associations reported to the ISC by regional agencies. Even after ISC data management is re-organised to make this possible, however, nearly half of all readings will require initial associations by the ISC. Noureddine is taking a flexible approach, creating a system that can be configured to treat readings from different stations or networks according to the characteristics of each. To decide the preferred association the new system will consider initial arrival times, S-P times, amplitude/magnitude consistency, and history of reporting to the ISC as a function of event magnitude and distance.

Royal Society Supplement

The UK Royal Society has provided a supplementary grant of nearly £20,000 to aid the ISC computer modernisation programme. Thanks to the Royal Society, installation of modern computers at the ISC is now largely completed. In part, the grant has enabled the ISC to purchase a Sun workgroup server and additional disks. The design of the server emphasises rapid access to files rather than processing power. Despite distribution of processing tasks and temporary file storage to individual workstations, a single computer remains responsible for the principal data files and most services, such as e-mail, the web site and the relational database. With the existing ISC data management system, many updates require reading the complete data file for a month and writing a replacement. The new server should improve performance for other users during these updates as well as speeding individual file accesses.

ISC and IUGG99

The XXII General Assembly of the IUGG will take place in Birmingham this July, less than 200 km from the ISC's home in Thatcham. The ISC is undertaking several activities to take advantage of this special opportunity to communicate directly with data contributors and users. One of these activities is an open house, giving seismologists an opportunity to better understand how the definitive global seismic bulletin is compiled. In order to offer this opportunity to as many seismologists as possible, the open house will be held the weekend between the two weeks of IUGG.

The ISC's activities for IUGG99 include presentations in the scientific programme by several ISC staff members. Alison Bird plans to discuss "Search" events - the earthquakes found by the ISC from unassociated readings. Noureddine Beghoul will describe how he plans to improve automatic association of events and readings, which is critically important as the number of readings continues growing. Anna Surguy plans to review the wide variety of ways to access ISC data, including CD's and the Internet, as well as the printed Bulletin. Dmitry Storchak will summarise comparisons of the ISC Bulletin with the bulletins of the US NEIC and the CTBT IDC. Ray Willemann will outline alternatives for the future of the ISC, which could include adoption of new travel-time tables, location algorithms, or earthquake parameters. The abstracts submitted by ISC staff are all available from our web site, at http://www.isc.ac.uk/iugg99.

Writing a Program to Retrieve ISC Data

Thousands of seismologists around the world have taken advantage of the ISC web site to retrieve data over the last year. But almost all of them have worked interactively with a web browser, even if one of their own programs had first decided just which data were needed. The ISC could better serve many users by providing a data access method that a computer program could use directly.

Dr Hans Israelsson at the CTBT Prototype IDC has found a way for Perl programmers, at least, to write programs that retrieve data using the interface that the ISC already provides.

The public domain Perl packages LWP and URI can help Perl programmers to exchange messages between computers using http (hypertext transfer protocol). Packages, as well as Perl itself, are available from the Comprehensive Perl Archive Network (CPAN) at web sites around the world. You can find the CPAN node nearest you from the CPAN link at http://www.perl.com/. Once Perl itself and the packages are all installed, the simple access program shown in the box below will retrieve ISC data.

Despite continued growth in data retrievals from the ISC web site, over a 3-day period Dr Israelsson is personally responsible for nearly 30% of all ISC Internet data accesses ever! It seems that Dr Israelsson has helped show the way to significant expansion in use of ISC data.

To make this type of retrieval more widely accessible, the ISC may add an interface to its web server that responds to AutoDRM data request messages. In addition, however, utilities in a variety of programming languages and for a variety of computers may be required. Meanwhile, seismologists whose programs are not written in Perl might consider creating a Perl utility and running it from scripts that also run their own data analysis programs.


#!/bin/perl

# Program to retrieve primary epicentres from the ISC 
# within 30 degrees of a given location on a given day

# Include the Perl packages for web communication
use LWP::Simple;
use URI::URL;

# Get time and location from the command line
($year, $mon, $day, $lat, $lon) = @ARGV;

# Select the ISC web site
$iscbull = 'http://www.isc.ac.uk/cgi-bin/bull-link?';

# Assemble the query
$yearmo = 'Year='.$year.'&Month='.$mon;
$start = '&start_day=&'.$day.'&start_hour=0';
$end = '&end_day='.$day.'&end_hour=23';
$center = '&ctr_lat='.$lat.'&ctr_lon='.$lon.';
$dist = '&max_dist=30&max_dist_units=deg';
$query = $iscbull.$yearmo.$start.$end.$center.$dist;

# Create the URL
$url = url("$query");

# Retrieve data from the ISC
$data = get($url);

# Print the data
print "$data\n";

Database Loading Underway

An important element of the ISC's effort to improve services is replacement of the existing data management system with a relational database. The objectives of the new data management are to ensure data integrity while several ISC seismologists edit the Bulletin simultaneously, make the ISC's historical, Bulletin and collected data accessible through a unified interface, and provide a reasonably quick response to ad-hoc queries spanning long time periods.

During the first quarter this year, the Centre took a big step forward by completing the design of the tables in its new database and loading its first complete month. The design is based on CSS 3.0, a design that has been adopted by seismic data agencies around the world. Adaptations specific to the ISC were required to represent collection of phase arrivals into reading groups and independent readings of the same seismic record.

Database administrator James Harris has written scripts that read files from the ISC CDs, and insert records in the appropriate database tables. Extensive checking of the loaded data is being carried out before re-writing ISC applications to work directly with the relational database.

SRL Paper on Regional Thresholds

Ray Willemann's paper in on regional thresholds of the ISC Bulletin has been accepted for publication in Seismological Research Letters and is scheduled for to appear in the May/June issue. For reprints write to the ISC by post or e-mail.

Annual Report

The annual Director's Report gives a look at work at the ISC over the past year and a summary of plans for upcoming years. The report summarising activity during 1998 is planned to be available from the ISC web site by mid-May.