Open AccessThe great March 25, 1998, Antarctic Plate earthquake: Moment tensor and rupture history
Author(s) -
Henry C.,
Das S.,
Woodhouse J. H.
Publication year - 2000
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2000jb900077
Subject(s) - intraplate earthquake , seismology , geology , epicenter , moment tensor , seismic moment , geodesy , moment magnitude scale , centroid , rake , mantle (geology) , geophysics , fault (geology) , geometry , mathematics , scaling , geomorphology , deformation (meteorology) , tectonics , oceanography
We use broadband body and mantle wave data to study the 1998 Antarctic intraplate earthquake. The centroid moment tensor (CMT) has a large non‐double‐couple component. There exist two pure double‐couple constrained solutions that fit the data almost equally well. The frequent practice of taking the “best double‐couple” gives a far from optimal solution. We use P and SH body waves to determine the rupture parameters of the first and larger of the two observed subevents. The best rupture plane, with strike 96°, dip 69°, and rake −18°, is compatible with only one of the two CMT solutions: strike 96°, dip 64°, rake −23°, centroid location (63.1°S, 148.4°E, 10 km depth), centroid time 0313:02 UT, and M 0 = 1.3 × 10 21 N m ( M w = 8.0). The first subevent is a simple, primarily westward propagating ∼140‐km rupture, of ∼45‐s duration, with average velocity ≳3 km s −1 ; it has a seismic moment of 1.2×10 21 N m ( M w = 8.0), with 75% of its moment released between 10 and 27 s, and a stress drop of ∼240 bars. The rupture is physically bounded by two fracture zones at 147.5°E and 150°E. The second subevent lasted from 70 to 90 s on a fault extending from 210 to 270 km west of the epicenter, with a moment of 0.3–0.6×10 21 N m ( M w = 7.6–7.8). This is a spectacular example of dynamic stress triggering over a 100‐km separation distance with a time delay of ∼40 s. The complex pattern of aftershocks is primarily controlled by preexisting fracture zones on the ocean floor.