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.