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ROBERTS, MATTHEW J  Physics Department, Icelandic Meteorological Office.
Stefánsson, Ragnar  Physics Department, Icelandic Meteorological Office.
Halldórsson, Páll  Physics Department, Icelandic Meteorological Office.

Iceland straddles the spreading, tectonic boundaries of the northeast Atlantic plate and the Eurasian plate. This situation promotes frequent earthquakes and volcanic eruptions due to elevated crustal stresses imposed by magma pressure. Hazardous earthquakes occur in two geographic regions: the south Iceland seismic zone and the Tjörnes fracture zone. Twenty active volcanoes reside on land and a further 10 exist in offshore regions; collectively, 229 observed eruptions have occurred since the ninth century. Although Iceland has a population density of just three persons per square kilometre, the direct effects of earthquakes and volcanic eruptions have caused at least 193 fatalities. Senor-based measurements of seismicity and ground deformation are fundamental to real-time monitoring and assessment strategies for nascent tectonic hazards. To enable accurate, short- and long-term factual statements about tectonic hazards, the Icelandic Meteorological Office (IMO) has developed an Internet-based early warning and information system (EWIS) for visualizing results from its national seismic network. Here we (i) outline the design of EWIS; and (ii) explain how EWIS facilitates real-time geoscience for hazard identification and risk reduction.

Telemetric methods deliver data from 41 seismometers to IMO in Reykjavík. Basic seismological parameters are computed at each seismic station before automated waveform analysis takes place at IMO. Earthquake magnitude and hypocentre data are available routinely a few minutes after an earthquake has occurred. We use GIS and Internet technology in tandem to unite seismological data with geological information in a Website environment. This approach allows synoptic views of past and present seismicity levels, thus providing a forecasting basis for earthquakes and volcanic eruptions. The EWIS Website also hosts a database, which comprises scientific publications, customised hazard summaries, pre-processed information for civil defence purposes, and annotated map and image resources. Although EWIS is utilised primarily by IMO, it also serves as a heuristic tool for scientific and public communication of geophysical information. Through Internet-based analyses of earthquake data, distinct, time-dependent changes in tectonic activity are apparent. For example, we observe that comparatively large earthquakes on bedrock faults can transmit stress changes to several fault-lengths distance, thereby mechanically triggering secondary earthquakes. By calculating the stress changes resulting from individual earthquakes, we are progressing toward a national map of expected earthquake intensities. The main strength of EWIS is the ease and speed at which multi-parameter historic and real-time seismic data can be visualized via the Internet. This synergy of information is fundamental to timely identification and assessment of tectonic hazards in Iceland.

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