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

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.

Interpreting ancient marine seismites and apparent epicentral areas for paleo-earthquakes, Middle Ordovician Lexington Limestone, central Kentucky

“…2), and the hardground at the base of the Brannon can be traced locally into the Tanglewood. At depth, these carbonates overlie the mid-Proterozoic East Continental Rift basin, a late Proterozoic-Middle Cambrian Iapetan rift, and the Grenville Front (Black, 1986;Shumaker, 1986;Drahovzal et al, 1992;Ettensohn and Pashin, 1992;Rast and Goodmann, 1995), all of which are reflected in a series of basement faults that are prone to reactivation right up to the present (e.g., Herrmann et al, 1982;Van Arsdale, 1986;Street et al, 1993). In fact, many of the extant fault systems in central Kentucky ( Fig.…”

Regional Magnitude Scaling, Transportability, and Ms:mb Discrimination at Small Magnitudes

“…VOSS and HERMANN (1980); t HASEGAWA (1983); u HASEGAWA and WETMILLER (1980); v BOATWRIGHT (1994); w ; x Harvard Centroid Moment Tensor (CMT); y STREET (1984); z ATKINSON (1993); aa SHIN and HERRMANN (1987); ab Tennessee Earthquake Information Center; ac International Seismic Center (ISC); ad CHAEL (1987); ae NABELEK and SUAREZ (1989); af KIM (1998); ag GLASSMOYER and BORCHERDT (1990); ah TAYLOR et al (1989); ai STREET et al (1993); aj SOMERVILLE et al (1990); ak LI et al (1995); al SHI et al (1998); am XIE (1998). This is a remarkable claim considering the large variations of crustal structures around the world, which might be expected to aect the source amplitude of Lg waves.…”