Geology topics
Publications and source records attributed to J.H. Whitcomb.
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There has been a continuing demand on the part of many persons, institutions, commercial companies, government agencies, and so forth for up-to-date maps and tables of earthquakes in southern California. Unfortunately, final catalogs of earthquakes such as Hileman and others (1973), Hill and others (1975a), and Friedman and others (1976) lag in publication as long as two years beyond the end of the recording periods which they cover, owing to the time-consuming process of re-reading seismograms to improve earthquake locations. It is, thus, the intent of this report to make public a preliminary version of the catalog(s) that will cover the period October 1976 -September 1977. This catalog is similar to that of Fuis and others (1977) which covers a prior period of time from June 1974 -September 1976. The three most serious problems with this catalog are 1) incomplete reporting of earthquake magnitudes, 2) use of more than one crustal model for locating earthquakes in a given area, and 3) inclusion of blasts. These problems will be corrected for the final catalog(s), but we felt that they should not hold up release of this preliminary catalog.
Seismological investigations show that the Point Mugu earthquake involved north-south crustal shortening deep within the complex fault zone that marks the southern front of the Transverse Ranges province. This earthquake sequence results from the same stress system responsible for the deformation in this province in the Pliocene through Holocene and draws attention to the significant earthquake hazard that the southern frontal fault system poses to the Los Angeles metropolitan area.
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