Composite focal mechanism for microearthquakes along the northeastern border of the Caribbean plate

Journal Article · Sat May 01 04:00:00 EDT 1982 · Geophys. Res. Lett.; (United States)

DOI:https://doi.org/10.1029/GL009i005p00511· OSTI ID:7042288

Frankel, A

Seismograms from a local seismic network in the Virgin Islands portion of the northeastern Caribbean are used to determine a composite focal mechanism for 26 microearthquakes along the North America--Caribbean plate boundary. Only one nodal plane of the focal mechanism could be constrained from P-wave first motion data alone. P/SV amplitude ratios observed for these events were compared to theoretical amplitude ratios calculated for different focal mechanisms. This procedure constrained the dip of the second nodal plane to be shallower than about 50/sup 0/, ruling out the possibility of a transform fault in this portion of the plate boundary. The resulting focal mechanism indicates that oblique underthrusting of the North American plate beneath the Caribbean plate occurs in the area. This oblique motion is accommodated along a thrust plane that dips at a relatively shallow angle beneath the Virgin Islands platform.

• Research Organization: Lamont-Doherty Geological Observatory and Department of Geological Sciences of Columbia University, Palisades, New York 10964
• OSTI ID: 7042288
• Journal Information: Geophys. Res. Lett.; (United States), Journal Name: Geophys. Res. Lett.; (United States) Vol. 9:5; ISSN GPRLA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
ATLANTIC OCEAN
BATHYMETRY
CARIBBEAN SEA
EARTHQUAKE FOCI
EARTHQUAKES
FEDERAL REGION II
ISLANDS
LESSER ANTILLES
MICROEARTHQUAKES
NORTH AMERICA
PLATE TECTONICS
SEAS
SEISMIC EVENTS
SEISMIC P WAVES
SEISMIC S WAVES
SEISMIC WAVES
SURFACE WATERS
TECTONICS
USA
VIRGIN ISLANDS
WEST INDIES