Software References

From data analyses such as polarity analysis of P and S waves, moment tensor inversion, etc, it is possible to obtain two nodal planes, the one of which is an actual earthquake fault. In order to determine which nodal plane is an actual earthquake fault, further analyses are necessary.  Aftershock distribution is often utilized to determine an earthquake fault, because aftershocks are expected to concentrate on and around it. Aftershock distribution can be determined by hypocenter determination technique for a single event, which is explained in Grade 1. Also, application of simultaneous determination of hypocenters such as Joint Hypocentral Determination (JHD. e.g., Pavlis and Booker, 1983; Pujol, 1988), MJHD (Hurukawa and Imoto, 1990, 1992) and HypoDD (Waldhauser & Ellsworth, 2000) is effective to obtain more precise estimates.  Hori (2004, manuscript can be found at http://www.bosai.go.jp/library/pub/report/PDF/65/65hori.pdf) proposed a procedure to determine an earthquake fault using a CMT solution and aftershock distribution. When the earthquake fault plane and its size are known, it is possible to employ attenuation equation using the distance between a position on the Earth�fs surface and the nearest point on the fault from it. Precise analyses of waveform data can also be used to determine an actual earthquake fault, which is mentioned in Grade 3.

The followings are available for simultaneous determination of hypocenters:         HypoDD               Related URL                    http://www.ldeo.columbia.edu/~felixw/hypoDD.html         JHD               Related URL                    ftp://www.orfeus-eu.org/pub/software/iaspei2003/8509pujol/readme_jhd.html

Felix Waldhauser and William L. Ellsworth, 2000. A Double-Difference Earthquake Location Algorithm: Method and Application to the Northern Hayward Fault, California, Bull. Seism. Soc. Am., 90, 1353-1368.  Hurukawa, N. and Imoto, M., 1990. Fine structure of an underground boundary between the Philippine Sea and Pacific plates beneath the Kanto district, Japan, Zisin (J. Seismol. Soc. Jpn.), 43, 413-429 (in Japanese with English abstract).  Hurukawa, N. and Imoto, M., 1992. Subducting ocenic crusts of the Philippine Sea and Pacific plates and weak-zone-normal compression in the Kanto district, Japan, Geophys. J. Int., 109, 639-652.  Pavlis, G. and Booker, J., 1983. Progressive multiple event location (PMEL), Bull. Seism. Soc. Am., 73, 1753-1777.  Pujol, J., 1988. Comments on the joint determination of hypocenters and station corrections, Bull. Seism. Soc. Am., 78, 1179-1189.