MOMENT TENSORS OF MICROEARTHQUAKES FROM THE EYJAFJALLAJOKULL VOLCANO IN SOUTH ICELAND

Analyses of relative P- and S-wave amplitudes of 15 selected earthquak es (M-L <2.3) from a seismic swarm, which occurred in May and June 199 4 at the Eyjafjallajokull volcano in South Iceland, reveal similar rad iation patterns, a thrust-type double-couple with an additional source component. All focal solutions have nearly vertical T-axes and horizo ntally oriented P-axes, with E-W-oriented nodal planes. The volume inc rease corresponding to an isotropic source component is estimated to b e in the range of 24 m(3). The temporal and spatial seismic pattern, s mall magnitude range, focal mechanisms and depth range of the Eyjafjal lajokull earthquakes indicate vertical intrusion of magma into a confi ned region at the northern flank of the volcano.