Uniformly processed strong earthquake ground accelerations in the Western United States of America for the period from 1933 to 1971: corrected acceleration, velocity and displacement curves, 1978

In this report we present corrected acceleration, velocity and displacement curves for recordings in the free-field or in basements of buildings. This data was recorded in the Western United States between 1933 and 1971.; Acceleration, velocity and displacement curves presented here differ from those presented in Volume II, Parts A through Y (Hudson, 1976). In those reports, a uniform frequency band between 0.07 Hz (or 0.125 Hz) and 25 Hz has been chosen for all records. In this report, each record is analyzed separately. Whenever the signal becomes smaller than the amplitude of average plus one standard deviation of digitization noise, the original low-frequency limit (0.07 Hz or 0.125 Hz) is replaced by a higher cut-off frequency to eliminate digitization and processing noise. For many records, this improves the accuracy with which computed velocity and displacement curves approximate actual ground motions.

本报告提供了针对自由场（free-field）或建筑物地下室中实测得到的校正后加速度、速度与位移曲线。该数据集于1933年至1971年间在美国西部采集录制。
本次呈现的加速度、速度与位移曲线，与第二卷A至Y分册（Hudson，1976）中所载的同类曲线存在差异。此前的报告中，所有实测记录均统一采用0.07 Hz（或0.125 Hz）至25 Hz的频带范围进行处理。本报告则对每一条记录单独开展分析：当信号幅值低于数字化噪声（digitization noise）均值加一倍标准差的阈值时，将原低频限值替换为更高的截止频率（cut-off frequency），以消除数字化与处理过程引入的噪声。针对多数记录而言，该处理方式可提升计算所得速度与位移曲线对实际地面运动的拟合精度。