INTERMAGNITUDE RELATIONSHIPS AND ASPERITY STATISTICS

被引:22
作者
GUSEV, AA
机构
[1] Institute of Volcanology, Petropavlovsk-Kamchatsky
[2] Institute of Volcanic Geology and Geochemistry, Petropavlovsk-Kamchatsky
关键词
MAGNITUDE; MOMENT MAGNITUDE; SATURATION OF MAGNITUDE; PEAK FACTOR; ASPERITY; SEISMIC FORCE; PARETO DISTRIBUTION;
D O I
10.1007/BF00878585
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Several data sources appeared recently which enable one to construct an updated version of global average intermagnitude relationships. A set of nonlinear magnitude vs M(w) (or log M(o)) curves is presented. Several regional scales are also included in the set. Utilization of M(w) as a referential scale provides the optimal basis for extrapolation of return periods, strong motion amplitudes and source parameters from moderate to large earthquakes. Remarkable features of the constructed curves are: (1) practical coincidence of modified m(b) (m(b)* or m(b)) scale with m(SKM) of the Soviet Seismological Service (except the constant shift of 0.18); (2) the lack of true saturation of all scales but m(b) with the possible exception of m(B) for M(w) > 8.7; (3) almost common shape of curves for all short-period magnitudes (global as well as regional); (4) lack of a systematic world-averaged difference between American and Soviet M(s). For M(o) large enough, m(MSK) (or m(b)*) vs log M(o) trend has the slope b = 0.35. Data are compiled to estimate short-period spectral level vs log M(o) trend, and its slope seems to be near beta = 0.39. These two values and some additional assumptions, rather common, lead to the following conclusions regarding properties of the earthquake source and its short-period radiation: (1) peak to rms amplitude ratio (peak factor) of a short-period record grows as M(o)0.11-0.13, hence the Gaussian noise model of the record (predicting M(o)0.03-0.04) can be definitely rejected, and some heavy-tailed peak distribution is to be assumed instead; (2) if one specifies this distribution to be the power-law (Pareto), then the estimate of the exponent-alpha for this distribution approaches 2 for short-period teleseismic records (and this alpha-value is the same as had been found previously for accelerogram peaks); (3) this may indicate the power law distribution of seismic force values of individual asperities; (4) there is a difference between our estimated beta = 0.39 and beta = 1/3 expected from the omega-2 model; data are not sufficient at present to show definitely that the difference is real.
引用
收藏
页码:515 / 527
页数:13
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