Abstract
The seismic moments (M(subscript o)), body-wave magnitudes (m(subscript b)), and surfacewave magnitudes (M(subscript s)) of 201 Taiwan earthquakes with 4.8≤m(subscript b)≤6.6 published in the Global CMT catalog from 1976 to 2006 are used to study the correlations among the three source parameters. The resultant relationships are: log(M(subscript o))=(1.07±0.04) M(subscript s)+(18.72±0.20); log(M(subscript o))=(1.73±0.09) m(subscript b)+(15.09 ± 0.52); and M(subscript s) = (1.46±0.08) m(subscript b)-(2.52±0.43). The three relationships have high agreement with those of earthquakes in the circum-Pacific seismic belt. This might imply that the tectonic conditions and source properties of the Taiwan region behave like the average ones of the circum-Pacific seismic belt. The relationships between the three source parameters and local magnitude are: log(M(subscript o))=(1.27±0.06) M(subscript L)+(17.23±0.35); m(subscript b)=0.66±0.03) M(subscript L)+(1.69±0.17); and M(subscript s)=(1.03±0.06) M(subscript L)-(0.53±0.36).
Highlights
Magnitude is regarded as the most directly measurable and simple parameter to specify quantitatively the size of an earthquake
The three relationships have high agreement with those of earthquakes in the circum-Pacific seismic belt. This might imply that the tectonic conditions and source properties of the Taiwan region behave like the average ones of the circum-Pacific seismic belt
The two source spectral models are briefly described below: at low frequencies, the spectral amplitude is almost proportional to the seismic moment; while at high frequencies, especially for higher than the corner frequency, the spectral amplitude is proportional to ω−2 for the former and ω−3 for the latter
Summary
Magnitude is regarded as the most directly measurable and simple parameter to specify quantitatively the size of an earthquake. Aki (1972) constructed the theoretical correlation for log(Mo) versus Ms His results show that log(Mo) exponentially increase with Ms. The two source spectral models are briefly described below: at low frequencies, the spectral amplitude is almost proportional to the seismic moment; while at high frequencies, especially for higher than the corner frequency, the spectral amplitude is proportional to ω−2 for the former and ω−3 for the latter. Kanamori and Anderson (1975) studied the correlation between these based on the ω−2 model, with a more reliable relation between fault length and duration time than that suggested by Aki (1972) Their results show log(Mo) ~ 1.5 Ms for common earthquakes and log(Mo) ~ 3 Ms for some events with long duration times.
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