Application of Distributed Object Technology to Seismic Waveform Distribution

Abstract

We develop a networked data distribution system for broadband seismic waveform data using Java RMI (Remote Method Invocation). Users can download data from various networks using a unified interface. There are two technical problems in building such a user-friendly system with a high capability for expansion: communication through firewalls and information synchronization between request interfaces. We solve these two problems using cgi (common gateway interface) filtering and the Directory Service, respectively. We are now distributing data from various Japanese broadband seismic networks (including PACIFIC21) together with data from BATS (Broadband Array in Taiwan for Seismology) and IRIS through the system. Digital seismic waveform data are being accumulated at an accelerating rate by various networks. Data analysis using these huge data sets is becoming increasingly common. For example, in the Western Pacific region, a large number of digital broadband seismographic stations have recently been installed by various institutions (Figure 1). If the data from these networks are appropriately combined, they effectively constitute a data set from a very dense broadband network. Such a data set should be very useful for determining seismic structure and earthquake source properties with high resolution. However, in the current waveform distribution system, such studies require somewhat tedious procedures for collecting the waveform data from different data centers, each of which has a different user interface. Looking at the field of computer science, distributed object technology (technology for distributing software modules to multiple computers on a network; The Object Management Group, 2000) is one of the most important technologies in modern system-programming practice, as it can handle a huge system in a straightforward manner. Java RMI (Gosling and Steele, 1996; Sun Microsystems, 1999) provides one of the most successful technologies to build a distributed object management system because of its high capability for expansion and security. …