At the western end of the Indian Ocean beneath the Arabian Sea the oceanic plate is being subducted beneath the Eurasian continental plate as it moves northward towards Iran and Pakistan, an area known as the Makran subduction zone.

 

Ocean floor sediments get scraped off and deposited at the subduction front, to create one of the largest accretionary wedges on Earth with more than 7km thickness of sediments.

 

None the less, it (at first) seems rather a quiet subduction zone, with relatively low seismicity and rather few historic earthquakes. One of the last ones of note occurred on November 28th 1945. A magnitude 8.1 quake, it triggered a submarine landslide that caused a 12-15 metre high tsunami resulting in the deaths of more than 4000 people along the Makran coast. It is the second worst tsunami event in the Indian Ocean, after the 2004 boxing day Sumatra earthquake.

 

The tsunami threat of the Makran subduction zone has been further highlighted in a paper in the latest issue of Geophysical Research Letters. A group of geophysicists from the National Oceanography Centre in Southampton, UK, have concluded that the Makran zone is capable of producing major earthquakes, up to magnitude 9.2. Any associated tsunami could be devastating to the coastal towns to the north, leading the authors to urge a re-assessment of the hazard in the region, and to survey possible historic and pre-historical evidence of past events.

 

The overall message appears to be that this region needs to pay attention to the threat from the sea, and that renewed studies of the Makran subduction zone and its historic behavior are called for.