Implications of spatial and temporal development of the aftershock sequence for the Mw 8.3 June 9, 1994 Deep Bolivian Earthquake

Stephen C. Myers, Terry C. Wallace, Susan Beck, Paul G. Silver, George Zandt, John Vandecar, Estela Minaya

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

On June 9, 1994 the Mw 8.3 Bolivia earthquake (636 km depth) occurred in a region which had not experienced significant, deep seismicity for at least 30 years. The mainshock and aftershocks were recorded in Bolivia on the BANJO and SEDA broadband seismic arrays and on the San Calixto Network. We used the joint hypocenter determination method to determine the relative location of the aftershocks. We have identified no foreshocks and 89 aftershocks (m > 2.2) for the 20‐day period following the mainshock. The frequency of aftershock occurrence decreased rapidly, with only one or two aftershocks per day occuring after day two. The temporal decay of aftershock activity is similar to shallow aftershock sequences, but the number of aftershocks is two orders of magnitude less. Additionally, a mb ∼6, apparently triggered earthquake occurred just 10 minutes after the mainshock about 330 km east‐southeast of the mainshock at a depth of 671 km. The aftershock sequence occurred north and east of the mainshock and extends to a depth of 665 km. The aftershocks define a slab striking N68°W and dipping 45°NE. The strike, dip, and location of the aftershock zone are consistent with this seismicity being confined within the downward extension of the subducted Nazca plate. The location and orientation of the aftershock sequence indicate that the subducted Nazca plate bends between the NNW striking zone of deep seismicity in western Brazil and the N‐S striking zone of seismicity in central Bolivia. A tear in the deep slab is not necessitated by the data. A subset of the aftershock hypocenters cluster along a subhorizontal plane near the depth of the mainshock, favoring a horizontal fault plane. The horizontal dimensions of the mainshock [Beck et al., this issue; Silver et al., 1995] and slab defined by the aftershocks are approximately equal, indicating that the mainshock ruptured through the slab.

Original languageEnglish (US)
Pages (from-to)2269-2272
Number of pages4
JournalGeophysical Research Letters
Volume22
Issue number16
DOIs
StatePublished - 1995

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Bolivia
aftershock
slabs
earthquakes
earthquake
Brazil
dipping
seismicity
slab
set theory
Nazca plate
occurrences
broadband
decay
foreshock
fault plane
dip

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

Cite this

Implications of spatial and temporal development of the aftershock sequence for the Mw 8.3 June 9, 1994 Deep Bolivian Earthquake. / Myers, Stephen C.; Wallace, Terry C.; Beck, Susan; Silver, Paul G.; Zandt, George; Vandecar, John; Minaya, Estela.

In: Geophysical Research Letters, Vol. 22, No. 16, 1995, p. 2269-2272.

Research output: Contribution to journalArticle

Myers, Stephen C. ; Wallace, Terry C. ; Beck, Susan ; Silver, Paul G. ; Zandt, George ; Vandecar, John ; Minaya, Estela. / Implications of spatial and temporal development of the aftershock sequence for the Mw 8.3 June 9, 1994 Deep Bolivian Earthquake. In: Geophysical Research Letters. 1995 ; Vol. 22, No. 16. pp. 2269-2272.
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