Discrepancies Between Prototype International Data Centre, International Seismological Centre & USGS Seismic Magnitudes
Technical rept. 30 Aug 2000-29 Aug 2002
COLUMBIA UNIV PALISADES NY LAMONT-DOHERTY EARTH OBSERVATORY
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A discrepancy between body-wave magnitudes, from the Prototype International Data Centre PIDC and the U.S. Geological Survey USGS, has persisted since 1995, and amounts to a few tenths of a magnitude unit. Since 1999 we have studied the discrepancy between magnitudes published by different agencies and this final report is comprised of two sections. The first, is a stand-alone paper published in the 2002 NovemberDecember issue of the Seismological Society of Americas Seismological Review Letters comparing the PIDC magnitudes with values assigned by a method that as closely as possible reproduces the Veith-Clawson protocol for reporting seismic body wave magnitudes. That protocol is the most clearly specified, or many different body-wave magnitude scales. The second section here, is a report which documents in detail the actual discrepancies between magnitudes assigned by three key agencies - namely, the USGS, the PIDC, and the International Seismological Centre ISC.