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The June 9 Bolivia and March 9 Fiji deep earthquakes of 1994: I. Source processes
Author(s) -
Lundgren Paul,
Giardini Domenico
Publication year - 1995
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 - 10.1029/95gl02233
Subject(s) - seismology , geology , focal mechanism , seismic moment , moment tensor , isotropy , moment magnitude scale , geodesy , point source , induced seismicity , physics , geometry , mathematics , deformation (meteorology) , optics , scaling , fault (geology) , oceanography
We examined the source characteristics of the 1994 deep earthquakes of Bolivia (June 9) and Fiji (March 9) over a period range of 1–1000 s using moment tensor and body wave analyses. Moment tensor inversions from 100–1000 s reveal that these two earthquakes were essentially point sources at very long period with insignificant isotropic and non‐double couple components with scalar moments M o = 2.56 × 10 21 Nm for the Bolivia and M o = 0.26 × 10 21 Nm for the Fiji earthquakes. Body wave analysis for the Bolivia event reveals a 45 s duration, a nearly linear E‐NE 1 km/s rupture on the subhorizontal focal mechanism plane giving a stress drop Δσ = 114 MPa. For the Fiji earthquake we find a change in focal mechanism and a linear 3 km/s rupture plunging shallowly to the north on the steep dipping nodal plane with a duration of at least 20 s and Δσ = 14 MPa. Both ruptures propagated parallel their null (σ 2 ) axis and suggests that their width is controlled by the thickness of the seismogenic volume in deep slabs.