The Southeastern Illinois Earthquake of 10 June 1987

1989 ◽  
Vol 60 (3) ◽  
pp. 101-110 ◽  
Author(s):  
K. B. Taylor ◽  
R. B. Herrmann ◽  
M. W. Hamburger ◽  
G. L. Pavlis ◽  
A. Johnston ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Surface Wave ◽  
Seismic Moment ◽  
Wave Amplitude ◽  
Main Shock ◽  
Source Parameters ◽  
Focal Depth ◽  
Precambrian Basement ◽  
Amplitude Spectra ◽  
Best Fit

Abstract The June 10 southeastern Illinois earthquake was the 11th largest earthquake felt in the central U.S. during this century. Source parameters of the main shock were estimated from an analysis of surface-wave amplitude spectra. The source that best fit the observed data has focal depth of 10 ± 1 km; mechanism with strike= 40.6°± 5.9°, dip= 76.2° ± 5.6°, slip= 159.7° ± 6.0°; tension and pressure axes of (T) trend= 357°, plunge= 24°, (P) trend= 89°, plunge= 4°; and a seismic moment of 3.1 * 1023 dyne-cm. With the combined efforts of six institutions, a 24-station analog microearthquake network was deployed around the main shock epicenter. One hundred eighty-five aftershocks were recorded in the first week of monitoring, providing 144 hypocenter determinations. A subset of 51 well recorded events was used for joint relocation and calculation of station corrections for the stations within 100 km of the main shock epicenter. Joint hypocenter locations differ only slightly from the original locations. The spatial distribution of well located aftershocks indicates that the rupture was confined to a pencil-like zone within the Precambrian basement, extending from 7 to 11 km depth.

The 4.6 mb,Lg Northeastern Kentucky Earthquake of September 7, 1988

1993 ◽  
Vol 64 (3-4) ◽  
pp. 187-199 ◽  
Author(s):  
R. Street ◽  
K. Taylor ◽  
D. Jones ◽  
J. Harris ◽  
G. Steiner ◽  
...  
Keyword(s):  
Surface Wave ◽  
Seismic Moment ◽  
Wave Amplitude ◽  
Linear Trend ◽  
Source Parameters ◽  
Strike Slip ◽  
Source Depth ◽  
Nodal Plane ◽  
Amplitude Spectra ◽  
Conjugate Fault

Abstract Source parameters for the September 7, 1988 northeastern Kentucky earthquake have been estimated from the analysis of surface-wave amplitude spectra. The source that best fits the observed data had a seismic moment of 2.0 × 1022 dyne-cm, a mechanism with strike = 198° ± 10°, dip = 51° ± 11°, and slip = −178° ± 17°, (T) trend = 160°, plunge = 25°, (P) trend = 55°, plunge = 28°, and source depth of 4 to 7 km. Thirty-two aftershocks were recorded during 2 weeks of monitoring following the mainshock; 23 of the aftershocks were locatable and fall on a roughly NW-SE linear trend. This trend is subparallel with the NW-SE nodal plane of the mainshock. Our analysis shows the 1988 event to be different from the July 27, 1980 mb,Lg = 5.3 earthquake located 11 km to the northwest. First, the 1988 event is considerably shallower (4 to 7 km) than the 1980 event (14 to 22 km). Second, data from the 1988 event suggest the motion is on a conjugate fault and is in contrast with the 1980 event, which had right-lateral strike-slip on a southeast-dipping plane.

Focal mechanism and source depth of earthquakes from body- and surface-wave data

1971 ◽  
Vol 61 (5) ◽  
pp. 1369-1379 ◽  
Author(s):  
Nezihi Canitez ◽  
M. Nafi Toksöz
Keyword(s):  
Surface Wave ◽  
Body Wave ◽  
Source Parameters ◽  
Focal Depth ◽  
Spectral Ratio ◽  
The Body ◽  
Spectral Ratios ◽  
Motion Data ◽  
Wave Data ◽  
Surface Wave Data

abstract The determination of focal depth and other source parameters by the use of first-motion data and surface-wave spectra is investigated. It is shown that the spectral ratio of Love to Rayleigh waves (L/R) is sensitive to all source parameters. The azimuthal variation of the L/R spectral ratios can be used to check the fault-plane solution as well as for focal depth determinations. Medium response, attenuation, and source finiteness seriously affect the absolute spectra and introduce uncertainty into the focal depth determinations. These effects are nearly canceled out when L/R amplitude ratios are used. Thus, the preferred procedure for source mechanism studies of shallow earthquakes is to use jointly the body-wave data, absolute spectra of surface waves, and the Love/Rayleigh spectral ratios. With this procedure, focal depths can be determined to an accuracy of a few kilometers.

Source mechanism of the Truckee, California, earthquake of September 12 1966

1970 ◽  
Vol 60 (4) ◽  
pp. 1199-1208 ◽  
Author(s):  
Yi-Ben Tsai ◽  
Keiiti Aki
Keyword(s):  
Seismic Moment ◽  
Additional Data ◽  
Focal Depth ◽  
P Wave ◽  
Eastern United States ◽  
Time Data ◽  
Travel Time Data ◽  
Amplitude Spectra ◽  
Plane Solution ◽  
Minimum Estimate

abstract With additional data on P wave polarities, the existing fault plane solution for the Truckee, California, earthquake of September 12 1966 (Ryall, Van Wormer and Jones, 1968) is revised to have the following strike and dip angles for its nodal planes: Strike Dip Plane A N 44°E 80°SE Plane B N 134°E 90° Nodal plane A is shown to agree very well with the aftershock zone determined by Greensfelder (1968). The observed Rayleigh and Love wave amplitude spectra from four WWSSN stations in the eastern United States are consistent with the revised solution, but not with the original one by Ryall et al. From these data, the focal depth and seismic moment of the earthquake are determined as 10 km and 0.83 × 1025 dyne-cm, respectively. The focal depth so obtained is the same as that determined from the near station travel time data by Ryall et al. The seismic moment is used to give a minimum estimate of about 30 cm for the average dislocation of the fault.

Source parameters of the June 13, 1967 earthquake near Lake Ontario, New York State

1977 ◽  
Vol 14 (11) ◽  
pp. 2651-2657 ◽  
Author(s):  
Michio Hashizume ◽  
Nagakoto Tange
Keyword(s):  
New York ◽  
Surface Wave ◽  
Epicentral Distance ◽  
Source Parameters ◽  
New York State ◽  
Focal Depth ◽  
Lake Ontario ◽  
Strike Slip ◽  
York State ◽  
Long Period

Source parameters of an earthquake with magnitude mb = 4.4 were determined by using surface waves. Small but clear surface wave signals were observed on long period records gathered from seismograph stations within an epicentral distance of about 2000 km. The focal mechanism was determined to be of strike-slip type with the maximum and the minimum compression axes trending NNW–SSE and ENE–WSW, respectively. The focal depth was determined to be near either 3 or 20 km.

Spectral and magnitude characteristics of anomalous Eurasian earthquakes

1977 ◽  
Vol 67 (2) ◽  
pp. 463-478
Author(s):  
So Gu Kim ◽  
Otto W. Nuttli
Keyword(s):  
Focal Mechanism ◽  
Rayleigh Waves ◽  
Main Shock ◽  
Focal Depth ◽  
P Wave ◽  
Wave Spectra ◽  
P Waves ◽  
Aftershock Sequences ◽  
Short Period ◽  
Amplitude Spectra

Abstract A number of main shock-aftershock sequences in the Eurasian interior contain some aftershocks whose mb:MS values are close to those of underground explosions. This paper is concerned with a study of the amplitude spectra of the P waves and Rayleigh waves for earthquakes of those main shock-aftershock sequences. It is found that for any given sequence studied, there is little if any variation in focal depth or focal mechanism. This rules out variations in these quantities as being the cause of anomalous mb:MS values. A study of the P-wave spectra establishes that one or both of the corner periods of anomalous earthquakes are smaller than those of non-anomalous earthquakes of the same moment. Thus the cause of anomalous mb:MS values of the earthquakes studied is a relative enrichment of the short-period portion of the spectrum of the anomalous events, which cannot be attributed to focal depth or focal mechanism.

Surface-Wave Amplitude Spectra

1972 ◽  
pp. 101-105
Author(s):  
V. I. Frantsuzova ◽  
A. L. Levshin ◽  
G. V. Shkadinskaya
Keyword(s):  
Surface Wave ◽  
Wave Amplitude ◽  
Amplitude Spectra
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