用近震尾波估算昆明及其周围地区的Q值和地震矩

本文应用推广了的Aki尾波理论模式,忽略震源频谱含量的影响,考虑到仪器系统和地球Q-滤波器对尾波频散的影响,计算了f_p-t^*和k-t^*独立的两套尾波响应理论量板。在假定Q与频率有Q（f）=Q₀（f/f₀）ⁿ关系的基础上,用云南区域台网短周期地震仪器记录的小震尾波资料,估算了昆明周围地区频率约1.0Hz的短周期波的地壳Q₀值。结果表明,该区的Q₀值在150-220之间,平均为191;频率相关值η不是常数,多数为0.2-0.3。这些结果与用尾波估算川滇交界地区的结果接近,表明云南地区的地壳Q₀值与美国西部地区类似,是属于低Q₀值地区。 此外,用尾波与地震矩建立的关系,提出用尾波估算地震矩的一种可能方法,讨论了该区震级与地震矩的经验关系。

Q VALUES AND SEISMIC MOMENTS ESTIMATES USING THE CODA WAVES OF NEAR EARTHQUAKES IN THE KUNMING AND SURROUNDING REGIONS

In this work, we have applied the expanded Aki's coda waves theory model, ignoring the effect of the source spectrum frequency content by considering the effect of the coda waves dispersion for the instruments system and the Q-filter of the earth. We have calculated two independent sets of response curves of coda waves "fp-t*" and "k-t*". A frequency dependence of Q is observed in the range of frequencies considered and a power law dependence of the form Q（f）=Q₀（f/f₀）η is assumed. On the basis of theoretical work, data are obtained from over 40 near earthquakes, with magnitudes mostly between 2.0 to 4.7. With seismograms recorded by 3 DD-1 and 4 VGK short-period seismographs in the Yunnan Province Seismic Networks, we estimated the crustal coda Q₀ values for frequencies near 1.0 Hz in the Kunming and surrounding regions. The results show that the average Q₀ value is 191. The values of frequency dependence η is not constant, with most η values between 0.2 to 0.3. These values are in fairly good agreement with short-period Q estimates made for those regions by Chen Peishan and Nuttli et al. （1984）, which are similar to those in the western United States （Singh and Herrmann, 1983）.In addition, we have attempted to determine the seismic moments from coda waves solely, and discuss the empirical statistical relationship between log M₀ and M₁ in the Kunming and surrounding regions.