In the Arabian Sea the 1,100 km long Owen fracture zone marks the boundary between the Indian and Arabian tectonic plates (see map). Both plates are colliding with the southern edge of Eurasia but the Arabian plate is generally considered to be moving north-eastward slightly faster than the Indian plate, and it is this difference in motion that is accommodated by the Owen fracture zone. This motion seems to have started between 3 and 8 million years ago.
The 3 March earthquake is marked with an orange coloured star on the USGS map of historic earthquakes shown below.
On this map the Sheba Ridge and the Owen transform fault down to the Carlsberg ridge are clearly delineated by historic earthquakes (1990 - present). Lesser earthquakes are seen along the Owen fracture zone (green line) - this is after all one of the slowest plate boundaries on Earth with a moving rate estimated as only about 2 mm/year. There is a conspicuous seismic gap in the southern end of “the green line” (marked with a question point on my map above) with some diffuse earthquakes West of the line.
Fournier et al. treated this area in a paper titled “In situ evidence for dextral active motion at the Arabia–India plate boundary” published in Nature Geoscience 1, 54 - 58 (2008) - Published online: 2 December 2007 | doi:10.1038/ngeo.2007.24 .
Their study suggest that a wedge of the Arabian plate, approximately corresponding to my orange coloured triangle, has been transferred to the Indian plate at some time in the last 10 million years. This is now a 50 km wide pull-apart basin, where an ultraslow divergent boundary (“spreading ridge”) has been developing. As the diffuse earthquakes seem to show the deformation is not yet clearly localised, but correspond to a transient state preceding the birth of a new plate boundary, and a new triple junction approximately where the earthquake on Monday occurred (orange star). A more stable ridge-ridge-ridge triple junction than the recent situation.