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Interface locking along the subduction megathrust from b ‐value mapping near Nicoya Peninsula, Costa Rica
Author(s) -
Ghosh Abhijit,
Newman Andrew V.,
Thomas Amanda M.,
Farmer Grant T.
Publication year - 2008
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 - 10.1029/2007gl031617
Subject(s) - subduction , geology , seismology , induced seismicity , slip (aerodynamics) , seamount , episodic tremor and slip , submarine pipeline , magnitude (astronomy) , tectonics , oceanography , physics , astronomy , thermodynamics
To understand controlling factors for seismogenesis and strain‐accumulation in subduction megathrusts we examine seismicity patterns across Nicoya, Costa Rica, to determine the overall and spatial variability in the earthquake frequency‐magnitude distribution along the interface. The mean reduction in earthquake activity with magnitude, b ‐value, is higher (1.06) than global subduction zone averages (0.6–0.8), suggesting the interface here is weakly coupled. Strong spatial variations in b are anticorrelated (−0.53) with geodetic estimates of interface locking of E. Norabuena et al. (2004). High b prevails in two regions, including the subducted Fisher seamount chain. A broad zone of reduced b is observed at and offshore the central Nicoya coast; extending towards an imaged locked patch. These results suggest b ‐value studies may be useful in identifying regions of increased interface locking in subduction zones, which may indicate regions capable of large slip in future large earthquakes.