Characteristics of Lg Wave Attenuation and Site Responsein North China Basin
Zhu Xinyun
Abstract：North China basin is one of the active seismic regions in the mainland of China.Studies of Lg wave attenuation and site responses can be used for tectonic interpretation,seismic hazard assessment and earthquake prediction.A combined inver-sion method based on seismic spectral ratios is an effective method for estimating attenuation and site responses.In this paper, a random resampling method is used to check stability of the solutions.Over 1 000 vertical seismograms with signal-to-noise ratio greater than two from 149 events were analyzed.The seismograms are recorded in the distance range of 100-600 km,the earthquakes occurred between 2004 and 2008 in the region and varied in magnitude between 1.7 and 5.3 (ML ).The ray-paths cover the region ranging from 38°N to 41°N and 114°E to 120°E.Fourier spectral amplitudes are measured from Lg phases win-dowed between the group velocity limits 2.60 and 3.65 km/s.The inversion is performed in a frequency range of 1-7 Hz with an interval of 0.2 Hz.The region displays low Q0 and a strong frequency dependence characterized by function Q=125 ± 4.4f0.86±0.03 .The result is consistent with the geology of the active tectonic region.The rock sites show small amplification. For soil sites,the amplification of low-frequency waves is higher than that for high-frequency waves.For the stations with more amplification,the corresponding error bar is great.This may indicate that the instability of the bases of these stations reduces the stability of the solution.
Keywords：site responseattenuationjoint inversionstability of solutionearthquakes
Publication Date：2016-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：10( 2109-2118 )