The data of short-period seismograms had been collected widely in the mainland area of China not including Xinjiang and Tibet. The physical quantities of Lg wave are determined respectively in the five subregions. The group velocities of priminary arrival and maximum amplitude of Lg wave are equal to 3.54±0.02 km/s and 3.30±0.05 km/s, respectively. The periods of Lg waves are between 0.2s to 1.2s, averaging 0.7s. The γ-values of Lg waves in the five subregions are equal to 0.0034±0.0001 km−1 for East, 0.0031±0.0004 km−1 for Southwest, 0.0027±0.0004 km−1 for Northeast, 0.0022±0.0001 km−1 for South, and 0.0021±0.0002 km−1 for Northwest subreqion, respectively. The average γ-value for the five subregions, γ=0.0027±0.0006 km−1. The relations among the amplitude ratioH/Z, the station correctionD z andD h of amplitudes, and among them and station site condition are discussed.
q(Δ) can be extended to the Xinjiang area.
Observation results show that: deviations among them Lg values determined by using Lg wave amplitudes (lgz, lgh, mxz andmxh); deviations that at station networks in unified and regionalm Lg; and deviations amongm Lg values determined in different provinces of the same sub-region, are generally smaller than 0.1 magnitude units. Them Lg scale basically maintains the magnitude level of the currentM L (CHN) between magnitude 2 and 6.
Key wordsattenuation group velocity amplitude ratio site effect Lg magnitude scale Chinese mainland
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