[en] This document presents a top level design of an Open Architecture Seismic Monitoring (OASM) system. The main components of the system are the time series processing, the event formation, the event classification and the hazard assessment modules. These fully independent modules are complemented by operational and research databases. Signal detection, onset time estimation and signal characterization are functions of the time series module. The detected signal association and event location are performed in the event formation module. The characterization of the seismic source, whether natural or artificial, is decided in the event classification module. The seismic hazard assessment module is the part of the system, where the basic parameters for use in seismic risk analysis are estimated. The operational database acts as the central facility through which access to the seismic data and communication between the system's modules are accomplished. The function of the research database is to provide scientists with a seismic bulletin and segmented waveforms for events through local and remote access via computer networks and dial-up telephone circuits. Although, the OASM system is designed to meet specific goals and objectives, its architecture is by no means limited to its current functionality. The first section of this report provides an overview and description of the components and data flow through the system. The second section presents the computational seismological techniques that form the foundation of the system. Only those techniques that are either essential to the design of the system or considered as uncommon signal processing tools are presented in this report. 67 refs