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.

本报告针对建筑物自由场（free-field）或地下室中的实测记录，提供修正后的加速度、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。
本报告所呈现的加速度、速度与位移曲线，与《第二卷 A至Y分册》（Hudson，1976）中刊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的频段范围。
本报告对每条记录单独开展分析：当信号幅值小于数字化噪声（digitization noise）平均值与一倍标准差（standard deviation）之和时，将以更高的截止频率（cut-off frequency）替换原有的低频限值（0.07 Hz或0.125 Hz），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。