However, because the earthquakes were oriented east west (the direction of the volcanic fault) and there was no volcanic tremor in seismometers distant from the seamount, Macdonald attributed the earthquake to faulting rather than a volcanic eruption.
Lineaments of microseismicity and source faults of large earthquakes are almost oriented in NNW SSE in the SSZ and oblique to the overall trend of the SSZ.
Considering the principal stress directions estimated by Matsumoto et al. (2013) shown in Fig. 6a, the similar nodal planes of the tremors and crustal earthquakes are favorably oriented under the current stress field.
Although the SSZ is characterized by active shallow microseismicity, each cluster of microseismicity and faults ruptured by recent large earthquakes are almost oriented in NNW SSE which is oblique to the overall trend of the SSZ.
Two of which, indicated by arrows in Figs. 8(a) and 8(b), were strike-slip earthquakes with P-axes oriented E-W and are completely different from subduction earthquakes along the seismic plane, which have T-axes oriented E-W.
This result is consistent with previous findings (e.g., Ukawa, 1982), according to which the intra-slab events are normal-fault or strike-slip type earthquakes, with the T -axis oriented in an E-W direction.
The isoseismals of this earthquake were nearly elliptical with a principal axis oriented in the ENE direction (Rajendran and Rajendran 2001; Yadav et al. 2008).
This earthquake had a thrust mechanism with a P-axis oriented E-W, consistent with the nature of the Kabaw Fault and completely different from intermediate-depth earthquakes in surrounding areas (see Fig. 8(a)), which have T-axes oriented E-W and record down-dip extension.
The CMT solutions for three of these earthquakes indicate strike-slip faulting with P-axes oriented E-W.
Two crustal earthquakes that occurred between the CCF and the Kaladan Fault north of 24.5°N show strike-slip faulting with P-axes oriented N-S, while two nearby earthquakes (between 92°E and 93°E) show reverse faulting with P -axes oriented E-W, similar to the characteristics of an earthquake that occurred near the Kabaw Fault.
The mechanisms of subduction earthquakes are down-dip extension, with T-axes oriented sub-parallel to the local dip of the slab.
