Fault-Plane Determination of the 18 April 2008 Mount Carmel, Illinois, Earthquake by Detecting and Relocating Aftershocks

Abstract

We developed a sliding-window cross-correlation (SCC) detection technique and applied the technique to continuous waveforms recorded by the Cooperative New Madrid Seismic Network stations following the 18 April 2008 Illinois earthquake. The technique detected more than 120 aftershocks down to M L 1.0 in the 2 week time window following the mainshock, which is three times more than the number of aftershocks reported by the seismic network. Most aftershocks happened within 24 hrs of the mainshock. We then relocated all events by the double-difference relocation algorithm. Accurate P-and S-wave differential arrival times between events were obtained by waveform cross correlation. After relocation, we used the L1 norm to fit all located events by a plane to determine the mainshock fault plane. The best-fit plane has a strike of 292° 11°and dips 81° 7°to the northeast. This plane agrees well with the focal mechanism solutions of the mainshock and four largest aftershocks. By combining the aftershock locations and focal mechanism solutions, we conclude that the 18 April earthquake occurred on a nearly vertical left-lateral strikeslip fault orienting in the west-northwest-east-southeast direction. The fault coincides with the proposed left-stepping Divide accommodation zone in the La Salle deformation belt and indicates reactivation of old deformation zone by contemporary stresses in the Midcontinent.Online Material: Local magnitudes, and new and catalog locations of the 2008 Illinois earthquake sequence.

Recent advances in imaging crustal fault zones: a review

“…1 A schematic plot of a typical fault zone, after Chester and Logan (1986) Pinto Mountain faults, Southern California (Fialko et al 2002). In addition, many geophysical methods have been applied in deriving FZ properties such as gravity and electromagnetic surveys, seismic reflection and refraction, travel-time tomography, earthquake location, waveform modeling of FZ-reflected body waves, FZ head waves, and FZ trapped waves (e.g., Mooney and Ginzburg 1986;BenZion and Malin 1991;Ben-Zion et al 1992;Hole et al 2001;Prejean et al 2002;Waldhauser and Ellsworth 2002;Li et al 2002;McGuire and Ben-Zion 2005;Bleibinhaus et al 2007;Li et al 2007;Yang et al 2009;Roland et al 2012). In the following, I briefly review a few seismological and geodetic methods that have been used to derive FZ structure.…”

Fault Orientation Determination for the 4 March 2008 Taoyuan Earthquake from Dense Near-Source Seismic Observations

“…Mori (1996) studied the foreshock (M w 4.3) source processes of the 1992 Joshua Tree Earthquake (M w 6.1) and concluded that a high static stress drop in this foreshock, from a rupture, propagated toward the hypocenter of the main shock. Yang et al (2009) relocated aftershocks and determined the fault plane of the 18 April 2008 Mount Carmel, Illinois earthquake. They concluded that the aftershock distribution was consistent with focal mechanism solutions for the main shock and the four largest aftershocks.…”

“…Allmann and Shearer (2007) identified a high-frequency secondary event buried on the rupture plane of the 2004 Parkfield earthquake and concluded that this event was located near the edge of a large asperity. It is recognized that detailed observation and analysis of moderate events should be helpful for understanding the fine structure of source ruptures and the micro-behaviors of earthquake sources physics (Mori 1996;Yang et al 2009). Such analyses can provide significant information relevant to debates on source scaling, stress drop and initial phases.…”

“…We employed waveform cross-correlation analysis (Yang et al 2009) and a double-difference earthquake location algorithm (Waldhauser and Ellsworth 2000) to determine the relative arrival times, improve the event locations and examine the rupture plane. The spatial distribution of aftershocks and the attitude of the rupture fault plane were determined from these analyses.…”

Seismicity of the Ste. Genevieve Seismic Zone Based on Observations from the EarthScope OIINK Flexible Array

“…The NMSZ has been a particular focus of attention for seismic studies in the central United States due to the three large M w > 7:0 earthquakes in 1811-1812 (e.g., Nuttli, 1973a;Dunn et al, 2010;Page and Hough, 2014). However, there is evidence of significant potential for large earthquakes outside the NMSZ, such as in the Wabash Valley seismic zone (WVSZ; Nuttli, 1979;Obermeier et al, 1991;Munson et al, 1992;Pavlis et al, 2002;Herrmann et al, 2008;Yang et al, 2009;Hamburger et al, 2011), the region near Marianna, Arkansas, southwest of the NMSZ (Tuttle et al, 2006), the region around the Meers fault, southwestern Oklahoma (e.g., Luza et al, 1987;Kelson and Swan, 1990), and the region northwest of the NMSZ around the Ste. Genevieve fault zone (Heinrich, 1937(Heinrich, , 1949Nuttli, 1973b).…”