The 9 December 2003 central Virginia earthquake sequence: A compound earthquake in the central Virginia seismic zone

Publication Type  Journal Article
Year of Publication  2005
Authors  Kim, W. Y.; Chapman, M.
Journal Title  Bulletin of the Seismological Society of America
Volume  95
Issue  6
Pages  2428-2445
Journal Date  Dec
ISBN Number  0037-1106
Accession Number  ISI:000234412100027
Key Words  eastern north-america; northeastern united-states; focal mechanism analyses; regional stress tensor; crustal structure; hylas zone; fault; seismograms; reflection; california
Abstract  

The 9 December 2003 central Virginia earthquake sequence was a compound earthquake consisting of two nearly identical events occurring about 12 see apart. The second event is separated by about 300 m from the first event along the azimuth of approximately 195 (+/- 10)degrees. The source mechanism determined from regional waveform inversion indicates predominantly thrust faulting at a depth of approximately 10 (+/- 2) km. The sequence with two events attained the combined seismic moment of M-0 2.64 (+/- 1.01) X 10(15) N m (M-w 4.3). The focal mechanism indicates a subhorizontal P axis trending 301 degrees and plunging 19 degrees. A regional stress model for the central Virginia seismic zone (CVSZ) derived from the 9 December 2003 events and 11 previous earthquakes indicates a thrust-faulting stress regime with a, trending 133 ( 12)degrees and plunging 14 ( 3)degrees. The least principal stress axis (sigma(3)) trends 25 (+/- 10)degrees and plunges 52 (+/- 3)degrees. The sigma(1) axis is rotated approximately 68 degrees clockwise relative to the average maximum horizontal compressional stress (S-Hmax) direction for eastern North America (approximately 65 degrees). The 9 December 2003 earthquake sequence occurred among the systems of Paleozoic and Mesozoic faults above the southern Appalachian decollement, which is at depths from 12 to 19 km in the Piedmont geologic province of central Virginia.

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999SZTimes Cited:0Cited References Count:64

URL  <Go to ISI>://000234412100027
DOI  Doi 10.1785/0120040207