Faulting Parameters of the January 16, 1994 Wyomissing Hills, Pennsylvania Earthquakes

Charles James Ammon, Robert B. Herrmann, Charles A. Langston, Harley Benz

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Two events dominated the January 1994, Wyomissing, PA earthquake sequence, an Mw 4.0 foreshock, followed by an Mw 4.6 mainshock. We modeled regional waveforms to estimate the event depth and the moment tensors for the two largest events in the sequence, and examine teleseismic wave-forms recorded on the ARCESS short-period seismic array to estimate the depth and source time function of the mainshock. Our data constrain the depth of the events to be shallower than 5 km, and prefer a depth of 3-5 km. For an assumed depth of 3 km, the mainshock moment tensor is 75% double couple, with (the major double couple) planes striking at 135°N, 347°N, dips of 49°, 46°, and rakes of 68°, 114°. The estimated moment is 8.9 × 1022 dyne-cm. The P axis strikes 241°N and plunges 2°, the Tension axis strikes 336°N and plunges 73°. The foreshock inversion results are virtually identical to the mainshock results; for a source depth of three km, we find a major double couple with a strike, dip, and rake of 121°N, 60°, and 66°, respectively. The seismic moment for the foreshock is 1.2 × 1022 dyne-cm, which is approximately 13% of the mainshock moment release. These events did not excite high-frequency Lg waves as effectively as typical eastern North American events, and the mainshock had a stress drop in the range of 25-50 bars.

Original languageEnglish (US)
Pages (from-to)261-269
Number of pages9
JournalSeismological Research Letters
Volume69
Issue number3
StatePublished - May 1998

Fingerprint

faulting
earthquakes
earthquake
foreshock
moments
rakes
moment tensor
dip
Lg-wave
tensors
teleseismic wave
time functions
seismic moment
estimates
parameter
waveforms
inversions

All Science Journal Classification (ASJC) codes

  • Earth and Planetary Sciences(all)

Cite this

Ammon, Charles James ; Herrmann, Robert B. ; Langston, Charles A. ; Benz, Harley. / Faulting Parameters of the January 16, 1994 Wyomissing Hills, Pennsylvania Earthquakes. In: Seismological Research Letters. 1998 ; Vol. 69, No. 3. pp. 261-269.
@article{f7d853b7e51a479380780d0aa86ee6c2,
title = "Faulting Parameters of the January 16, 1994 Wyomissing Hills, Pennsylvania Earthquakes",
abstract = "Two events dominated the January 1994, Wyomissing, PA earthquake sequence, an Mw 4.0 foreshock, followed by an Mw 4.6 mainshock. We modeled regional waveforms to estimate the event depth and the moment tensors for the two largest events in the sequence, and examine teleseismic wave-forms recorded on the ARCESS short-period seismic array to estimate the depth and source time function of the mainshock. Our data constrain the depth of the events to be shallower than 5 km, and prefer a depth of 3-5 km. For an assumed depth of 3 km, the mainshock moment tensor is 75{\%} double couple, with (the major double couple) planes striking at 135°N, 347°N, dips of 49°, 46°, and rakes of 68°, 114°. The estimated moment is 8.9 × 1022 dyne-cm. The P axis strikes 241°N and plunges 2°, the Tension axis strikes 336°N and plunges 73°. The foreshock inversion results are virtually identical to the mainshock results; for a source depth of three km, we find a major double couple with a strike, dip, and rake of 121°N, 60°, and 66°, respectively. The seismic moment for the foreshock is 1.2 × 1022 dyne-cm, which is approximately 13{\%} of the mainshock moment release. These events did not excite high-frequency Lg waves as effectively as typical eastern North American events, and the mainshock had a stress drop in the range of 25-50 bars.",
author = "Ammon, {Charles James} and Herrmann, {Robert B.} and Langston, {Charles A.} and Harley Benz",
year = "1998",
month = "5",
language = "English (US)",
volume = "69",
pages = "261--269",
journal = "Earthquake Notes - Seismological Society of America, Eastern Section,",
issn = "0895-0695",
publisher = "Seismological Society of America",
number = "3",

}

Faulting Parameters of the January 16, 1994 Wyomissing Hills, Pennsylvania Earthquakes. / Ammon, Charles James; Herrmann, Robert B.; Langston, Charles A.; Benz, Harley.

In: Seismological Research Letters, Vol. 69, No. 3, 05.1998, p. 261-269.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Faulting Parameters of the January 16, 1994 Wyomissing Hills, Pennsylvania Earthquakes

AU - Ammon, Charles James

AU - Herrmann, Robert B.

AU - Langston, Charles A.

AU - Benz, Harley

PY - 1998/5

Y1 - 1998/5

N2 - Two events dominated the January 1994, Wyomissing, PA earthquake sequence, an Mw 4.0 foreshock, followed by an Mw 4.6 mainshock. We modeled regional waveforms to estimate the event depth and the moment tensors for the two largest events in the sequence, and examine teleseismic wave-forms recorded on the ARCESS short-period seismic array to estimate the depth and source time function of the mainshock. Our data constrain the depth of the events to be shallower than 5 km, and prefer a depth of 3-5 km. For an assumed depth of 3 km, the mainshock moment tensor is 75% double couple, with (the major double couple) planes striking at 135°N, 347°N, dips of 49°, 46°, and rakes of 68°, 114°. The estimated moment is 8.9 × 1022 dyne-cm. The P axis strikes 241°N and plunges 2°, the Tension axis strikes 336°N and plunges 73°. The foreshock inversion results are virtually identical to the mainshock results; for a source depth of three km, we find a major double couple with a strike, dip, and rake of 121°N, 60°, and 66°, respectively. The seismic moment for the foreshock is 1.2 × 1022 dyne-cm, which is approximately 13% of the mainshock moment release. These events did not excite high-frequency Lg waves as effectively as typical eastern North American events, and the mainshock had a stress drop in the range of 25-50 bars.

AB - Two events dominated the January 1994, Wyomissing, PA earthquake sequence, an Mw 4.0 foreshock, followed by an Mw 4.6 mainshock. We modeled regional waveforms to estimate the event depth and the moment tensors for the two largest events in the sequence, and examine teleseismic wave-forms recorded on the ARCESS short-period seismic array to estimate the depth and source time function of the mainshock. Our data constrain the depth of the events to be shallower than 5 km, and prefer a depth of 3-5 km. For an assumed depth of 3 km, the mainshock moment tensor is 75% double couple, with (the major double couple) planes striking at 135°N, 347°N, dips of 49°, 46°, and rakes of 68°, 114°. The estimated moment is 8.9 × 1022 dyne-cm. The P axis strikes 241°N and plunges 2°, the Tension axis strikes 336°N and plunges 73°. The foreshock inversion results are virtually identical to the mainshock results; for a source depth of three km, we find a major double couple with a strike, dip, and rake of 121°N, 60°, and 66°, respectively. The seismic moment for the foreshock is 1.2 × 1022 dyne-cm, which is approximately 13% of the mainshock moment release. These events did not excite high-frequency Lg waves as effectively as typical eastern North American events, and the mainshock had a stress drop in the range of 25-50 bars.

UR - http://www.scopus.com/inward/record.url?scp=0031666001&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031666001&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0031666001

VL - 69

SP - 261

EP - 269

JO - Earthquake Notes - Seismological Society of America, Eastern Section,

JF - Earthquake Notes - Seismological Society of America, Eastern Section,

SN - 0895-0695

IS - 3

ER -