EARTHQUAKE PREDICTION RESEARCH IN THE SOUTH ICELAND SEISMIC ZONE AND THE SIL PROJECT

The South Iceland Lowland (SIL) project, started in 1988, is a concert ed effort of the Nordic countries toward earthquake prediction researc h in the South Iceland seismic zone (SISZ), where most destructive ear thquakes in the history of iceland have occurred. The zone has many ch aracteristics of a transform zone and takes up east-west relative moti on between two offset branches of the mid-Atlantic rift zone; i.e., th e eastern volcanic zone of Iceland and the Reykjanes Ridge. Earthquake s in this area reach the magnitude of roughly 7 and tend to culminate in sequences with duration from a few days to a few years. These event s are associated with right-lateral faulting on N - S striking faults arranged side-by-side along the E - W trending zone. Thus, apparently the general left-lateral transform motion is accommodated by countercl ockwise rotation of the fault blocks. The seismogenetic crust is 10 to 45 km thick and is underlain by partially molten mantle material. Ear thquake swarms, slowquakes, and strain episodes are commonly observed in the zone and in its proximity. The SIL project started with the con struction of a seismic network for near-real time data acquisition. Th e network has been collecting data since the beginning of 1990, and it has a nearly complete record down to magnitude 0 earthquakes inside t he area. Besides epicenter location and magnitudes the system automati cally computes fault plane solutions and dynamic source parameters. Fi rst results indicate good consistency between expected regional deviat oric stresses and stress release in microearthquakes as recorded and e valuated in the SIL system.