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The opening of the Andaman Sea: Where is the short‐term displacement being taken up?
Author(s) -
GuzmánSpeziale Marco,
Ni James F.
Publication year - 1993
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/93gl03053
Subject(s) - geology , seismology , fault (geology) , transform fault , term (time) , geodesy , physics , quantum mechanics
The short‐term spreading velocity in the Andaman Sea, a marginal basin inboard of the Western Sunda Arc, is calculated using the strain rate tensor which, in turn, is obtained from summing seismic moment tensors of normal‐faulting earthquakes. A velocity of displacement is also obtained for the right‐lateral Sagaing Fault, which is the northern continuation of the Andaman spreading system. Using earthquakes in a 22‐year period (1964–1986), the maximum spreading velocity in the Andaman Sea is found to be oriented in a N 19° W direction, with a speed of 0.05 cm/yr. The north‐south relative velocity along the Sagaing Fault is 0.5 cm/yr, for strike‐slip earthquakes between 1971 and 1992. Historical earthquakes in the Andaman Sea do not significantly add to the short‐term spreading velocity because there are no earthquakes with M s ≥6.0. For the Sagaing Fault, however, when moment tensors from earthquakes since 1908 are used, the relative velocity is 5.7 cm/yr, a figure close to the 3.72 cm/yr long‐term (13 ma) rate of opening of the Andaman Sea. These results suggest that strain due to the opening of the Andaman Sea is seismic along the Sagaing Fault and aseismic along the Andaman Sea Spreading System, probably because the spreading centers and transform faults in the Andaman Sea are short and cannot accomodate large earthquakes.