SINGLE AND JOINT FAULT PLANE SOLUTIONS FOR MICROEARTHQUAKES IN SOUTH ICELAND

We obtain fault plane solutions for a swarm of twelve events and two s ingle events ranging in magnitude between -0.3 and 3.1. The events wer e recorded by a local network in South Iceland, consisting of eight th ree-component stations with approximately 30 km between the stations. For events larger than M(L) congruent-to 1 the solutions are well cons trained. The non-uniqueness of the fault plane solutions increases wit h diminishing magnitude. To enhance the uniqueness of the fault plane solutions for the earthquake swarm, we search for mechanisms with a co mmon fault plane but possibly varying slip directions in that plane. D ata for all the events are consistent with faulting on a common plane. Relative location of the events shows that they all occurred less tha n 11 m from a single plane. Fault plane solutions for all the analysed events of the swarm, as well as the two single events, are consistent with strike-slip-dominated faulting on faults striking roughly north- south. The results are in agreement with the strikes of mapped surface fractures and focal mechanisms of larger earthquakes in the area. Thi s indicates that the microseismicity is related to the same pattern of regional deformation as the major earthquakes in South Iceland.