STRONG MOTION PREDICTION AND DESTRUCTIVITY EVALUATION FOR AN INHOMOGENEOUS SEDIMENTARY BASIN BASED ON THE UNDERGROUND STRUCTURE AS ESTIMATED FROM MICROTERMOR OVSERVATIONS

我们研究了最近提出的一种微震勘探方法——暂定名为扩大亨斯特里奇方法——在半径达600米的大型地震仪阵列上的实际适用性，以一种相当简单的方式获得s波速度结构，这是代表地下结构的最重要参数之一。放大Henstridge方法允许人们通过沿圆周放置至少3个位置的地震仪阵列来测量微震，从而获得表面波相速度的色散曲线，其特点是不需要在圆心放置地震仪，并且允许地震仪沿圆周间距不均匀。该方法的适用性已经证明了半径为5米和15米的阵列，但它从未被应用于更大的阵列。为了研究扩大亨斯特里奇方法在由3个台站组成的大型阵列中的实际适用性，我们在已知地下结构的位置进行了微震动探测，通过沿半径25至600米的圆周均匀或不均匀间隔部署3个地震仪的圆形阵列。我们首先用4个台站组成的阵列来测量微震，或者3个台站在圆周上几乎相等的间隔加上圆心上的第4个台站，并利用SPAC方法对所获得的数据估计了观测点下方的频散曲线a。然后，我们利用3个均匀或不均匀间隔的台站阵列，用扩大Henstridge法估计了色散曲线，并将分析结果与SPAC法估计的色散曲线进行了比较，以检验分析结果的充分性。我们发现，在分析结果的准确性方面，放大Henstridge方法与SPAC方法相当，并且与SPAC方法相比，可以充分评估色散曲线的波长范围倾向于向更长的波长移动。地震仪间距的不均匀会通过观测误差等因素影响频散曲线的估计精度。我们从经验上研究了台站配置的可容忍不均匀程度，在这种情况下，很可能获得适当的色散曲线，以及在这种情况下获得适当色散曲线的波长范围。少

We investigated the practical applicability, to large arrays of seismometers with radii up to 600 meters, of the tentatively named Enlarged Henstridge method, a recently proposed method of microtremor exploration to obtain, in a fairly simple way, the S-wave velocity structure which in one of the most important parameters to represent the underground structure. The Enlarged Henstridge method, which allows one to obtain the dispersion curve of the phase velocity of surface waves by measuring microtremors with an array of seismometers placed at least 3 locations along a circumference, is characterized by the lack of necessity to place a seismometer at the center of the circle and by the tolerance for uneven spacing of seismometers along the circumference. The applicability of the method had been demonstrated for arrays with radii of 5 and 15 meters, but it had never once been applied to larger arrays. In order to investigate the practical applicability of the Enlarged Henstridge Method t … More o large arrays consisting of 3 stations, we conducted an exploration of microtremors, at a location where the underground structure is known, by deploying circular arrays of 3 seismometers spaced at even or uneven intervals along circumferences 25 to 600 meters in radius.We first measured microtremors with an array of 4 stations, or 3 stations spaced at nearly equal intervals along a circumference plus a fourth station at the center of the circle, and estimated the dispersion curve a beneath the observation site by applying the SPAC method to the data obtained. We then estimated the dispersion curve with the Enlarged Henstridge method by using arrays of 3 evenly or unevenly spaced stations, and examined the adequacy of the analysis results by comparing them with the dispersion curve as estimated with the SPAC method. We found that the Enlarged Henstridge method was comparable to the SPAC method in terms of the accuracy of the analysis results, and that the wavelength range, over which the dispersion curve could be evaluated adequately, tended to shift toward longer wavelengths as compared with the case of the SPAC method.Uneven spacing of seismometers has influences, by way of observation errors and other factors, on the estimation accuracy for the dispersion curve. We empirically investigated the tolerable extent of unevenness in the configurations of the stations for which appropriate dispersion curves could be obtained with a high likelihood, as well as the wavelength ranges over which those appropriate dispersion curves were obtained in that case. Less