Geophysical investigations of the Western Ohio-Indiana region: Volume 7, Annual report, October 1987--September 1988

Technical Report · Thu Dec 01 04:00:00 EST 1988

OSTI ID:6495406

Schwartz, S Y; Lay, T; Young, C J

Earthquake activity in the Western Ohio--Indiana region has been monitored with a precision seismograph network consisting of nine stations located in west-central Ohio and four stations located in Indiana. No local earthquakes have been recorded during this report period. The low level of local seismicity in the last two years suggests that the occurrence of the m/sub b/ = 4.5 earthquake, in St. Marys, Ohio, on July 12, 1986, released most of the crustal strain accumulated. Four regional events were well recorded by the array stations during this year. Their magnitudes range from m/sub bLg/ = 3. 2--4.5. The largest of these events (7 September 1988 in northeastern Kentucky, m/sub b/ = 4.5) had minor damage reported. Upper mantle P wave (P/sub n/) velocities beneath the array stations have been investigated using relative time differences of arrivals recorded by stations located at similar back azimuth from given regional earthquake epicenters. Apparent P/sub n/ velocities determined from arrival times of earthquakes in northeastern Ohio (back azimuths of 50--70/degree/) reveal similar values to those obtained from earthquakes in southern Illinois and southeastern Missouri (back azimuths of 230--250/degree/). Comparable apparent P/sub n/ velocities obtained for rays traveling both to the northeast and to the southwest requires that the Moho not dip in either of these directions beneath the stations. The average P/sub n/ velocity of 8.41 km/s is similar to the values of 8.5 and 8.4 km/s that we obtained previously from the slope of P/sub n/ travel time curves constructed for earthquakes from northeastern Ohio and southeastern Illinois respectively. These values were slightly higher than the value of 8.2 km/s obtained previously from earthquakes in southwestern Indiana, northeastern Kentucky, and northeastern Missouri. 13 refs., 11 figs., 5 tabs.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (USA). Office of Nuclear Regulatory Research
• OSTI ID: 6495406
• Report Number(s): NUREG/CR-3145-Vol.7; ON: TI89007732
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
99 GENERAL AND MISCELLANEOUS
990220 -- Computers
Computerized Models
& Computer Programs-- (1987-1989)
COMPUTER NETWORKS
DOCUMENT TYPES
EARTHQUAKES
FEDERAL REGION IV
FEDERAL REGION V
FEDERAL REGION VII
ILLINOIS
INDIANA
KENTUCKY
MEASURING INSTRUMENTS
MISSOURI
NORTH AMERICA
OHIO
PROGRESS REPORT
SEISMIC ARRAYS
SEISMIC DETECTORS
SEISMIC EVENTS
SEISMIC P WAVES
SEISMIC WAVES
SEISMICITY
SEISMOGRAPHS
USA
VELOCITY