![]() Only authoritative for global seismicity for which there is no Mww, Mwc, Mwb or Mwr, typically 4.0-5.5 range. Reported for most M4.0-4.5 to 6.5 EQs that are observed teleseismically. Waveforms are shaped to the WWSSN SP response. Where A is the amplitude of ground motion (in microns) T is the corresponding period (in seconds) and Q( D, h) is a correction factor that is a function of distance, D(degrees), between epicenter and station and focal depth, h (in kilometers), of the earthquake.īased on the amplitude of 1st arriving P-waves at periods of about 1 s. Ms_20 tends to saturate at about M8.3 or larger. Authoritative for 6), shallow events, providing secondary confirmation on their size. Source complexity and dimensions at larger magnitudes (~M7.0 or greater) generally limits applicability. Only authoritative if Mww and Mwc are not computed.īased on the scalar seismic-moment of the earthquake, derived from moment tensor inversion of the whole seismogram at regional distances (~10-100 s pass band based on size of EQ). Source complexity at larger magnitudes (~M7.5 or greater) generally limits applicability. ![]() Generally computable for all M5.5 or larger events worldwide. Only authoritative if Mww is not computed, not published otherwise.ĭerived from moment tensor inversion of long-period (~20-200 s pass band based on size of EQ) body-waves (P- and SH). ![]() Generally computable for all M6.0 worldwide using primarily the Global Seismograph Network. M W = 2/3 * (log 10(M O) - 16.1), where M O is the seismic moment.ĭerived from a centroid moment tensor inversion of the long-period surface waves (~100-2000 s pass band based on size of EQ). Authoritative USGS magnitude if computed. Provides consistent results to M~4.5 within a regional network of high-quality broadband stations. Computed for all M5.0 or larger earthquakes worldwide, but generally robust for all M5.5 worldwide. If using metric units (N.m), the constant is 9.1.ĭerived from a centroid moment tensor inversion of the W-phase (~50-2000 s pass band based on size of EQ). Note this is also unit-dependent the formula above is for moment in dyne-cm. Mww (Moment W-phase)(generic notation Mw) ![]()
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