The Copala, Guerrero, Mexico Earthquake of September 14, 1995 (Mw=7.4): A Preliminary Report

Rapid Derivation of Rupture History for Large Earthquakes

“…The P-wave seismic moment estimated by the NEIC is 1.8 X 10 27 dyne-em. This value is identical to the centroid moment computed by Harvard but is 28-38 percent lower than the moments estimated by the University ofTokyo and the University of Michigan (see Anderson et al, 1995).…”

A Double Seismic Front and Earthquake Cycles Along the Coast of Oaxaca, Mexico

“…Within this context the 1928, 1937, and 1950 events break a first front (FF) of the area of contact between the two plates, and the 1968, 1982, and 1995 events break a second front (SF), which is located nearer the trench. The depth reported for 1968 event is 16 km (Chael and Stewart, 1982); for 1982 events are 15 and 20 km (Astiz and Kanamori, 1984), and for 1995 the depth is 15 km (Anderson et al, 1995). Although the 1928Although the , 1937, and 1950 earthquakes have been considered as "shallow" by many authors, the only report about depth is from Singh and Mortera (1991) who give depths between 10 and 20 km.…”

“…From Table 2 and Figure 3 it is possible to observe that none of the earthquakes in Zone 8 in the last 80 years have the same epicenter; even the aftershock areas of the 1968, and 1995events (Chael and Stewart, 1982Jimenez et al, 1983;Lermo, personal communication) do not overlap. This suggests that there are at least 6 asperities or seismogenic units in Zone 8, or 7 asperities if we consider the doublet of 1982 as resulting from failure on two different asperities.…”

Single-Station Earthquake Characterization for Early Warning

“…Many early warning systems use a network of seismic instruments to determine earthquake magnitude and location (Anderson et al, 1995;Espinosa-Aranda et al, 1995;Wu et al, 1998;Wu and Teng, 2002;Allen and Kanamori, 2003;A. Lockman and R. M. Allen, unpublished manuscript, 2005), but here we focus on a single seismic station's ability to assess earthquake hazard using the first few seconds of the P wave by calculating three parameters needed for early warning: event magnitude, hypocentral distance, and backazimuth.…”

“…The Seismic Alert System in Mexico City uses the peak ground motion measured near the Guerro Gap subduction zone to estimate magnitude, *Present address: Department of Earth and Planetary Science, University of California, Berkeley,307 McCone Hall,Berkeley,rallen@berkeley.edu. and conveys this information to the population in Mexico City, 300 km away, providing 60 sec or more warning of the impending ground motion (Anderson et al, 1995;Espinosa-Aranda et al, 1995). The Central Weather Bureau of Taiwan operates in a similar fashion, and can give a magnitude estimate about 22 sec after the P wave is detected and issue a warning to populations greater than 75 km from the epicenter (Wu et al, 1998;Wu and Teng, 2002).…”