The Mw 7.5 2009 Coco earthquake, north Andaman region

Mahesh, P. ; Bansal, Amit ; Kundu, B. ; Catherine, J. K. ; Gahalaut, V. K. (2011) The Mw 7.5 2009 Coco earthquake, north Andaman region Journal of the Geological Society of India, 77 (3). pp. 243-251. ISSN 0016-7622

Full text not available from this repository.

Official URL:

Related URL:


The recent 10 August 2009 Coco earthquake (Mw 7.5), the largest aftershock of the giant 2004 Sumatra Andaman earthquake, occurred within the subducting India plate under the Burma plate. The Coco earthquake nucleated near the northwestern edge of the 2004 Sumatra-Andaman earthquake rupture under the unruptured updip segment of the plate boundary interface. The earthquake with predominant normal motion on approximately north-south to northeast-southwest oriented plane is very similar to the 27 June 2008 Little Andaman earthquake which occurred in the South Andaman region near the trench. We provide the only available estimate of coseismic offset due to the 2009 Coco earthquake at a survey-mode GPS site in the north Andaman, located about 60 km south of the Coco earthquake epicentre. The not so large coseismic displacement of about 2 cm in the ESE direction is consistent with the earthquake focal mechanism and its magnitude. We suggest that, like the 2008 Little Andaman earthquake, this earthquake too occurred on one of the approximately north-south to northeast-southwest oriented steep planes of the obliquely subducting 90°E ridge which was reactivated in normal motion after subduction, under the favourable influence of coseismic and ongoing postseismic deformation due to the 2004 Sumatra-Andaman earthquake. Another notable feature of this earthquake is its relatively low aftershock productivity. We suggest that the earthquake occurred very close to the aseismic region of the Irrawaddy frontal arc of very low seismicity where pre-existing faults are not so critically stressed and because of which the earthquake could trigger only a few aftershocks in its immediate vicinity.

Item Type:Article
Source:Copyright of this article belongs to Springer Verlag.
Keywords:2004 Sumatra Andaman Earthquake; Andaman-Sumatra Subduction Zone; GPS Measurements; 90°E Ridge
ID Code:113223
Deposited On:07 Jun 2018 09:36
Last Modified:07 Jun 2018 09:36

Repository Staff Only: item control page