Earthquake prediction research in the South Iceland seismic zone and the SIL project

Abstract

The South Iceland Lowland (SIL) project, started in 1988, is a concerted effort of the Nordic countries toward earthquake prediction research in the South Iceland seismic zone (SISZ), where most destructive earthquakes in the history of iceland have occurred. The zone has many characteristics of a transform zone and takes up east-west relative motion between two offset branches of the mid-Atlantic rift zone; i.e., the eastern volcanic zone of Iceland and the Reykjanes Ridge. Earthquakes 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 events 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 counterclockwise rotation of the fault blocks. The seismogenetic crust is 10 to 45 km thick and is underlain by partially molten mantle material. Earthquake swarms, slowquakes, and strain episodes are commonly observed in the zone and in its proximity. The SIL project started with the construction of a seismic network for near-real time data acquisition. The network has been collecting data since the beginning of 1990, and it has a nearly complete record down to magnitude 0 earthquakes inside the area. Besides epicenter location and magnitudes the system automatically computes fault plane solutions and dynamic source parameters. First results indicate good consistency between expected regional deviatoric stresses and stress release in microearthquakes as recorded and evaluated in the SIL system.