During the 1966 Parkfield, California, earthquake a strong motion accelerograph and an adjacent seismoscope were located essentially at the causative fault. The accelerograph component parallel to the fault malfunctioned and left no recorded trace. The seismoscope record and the component of the ground motion perpendicular to the fault are used to reconstruct the acceleration component in the direction parallel to the fault. The details of the derived acceleration parallel to the fault differ from the past recorded strong ground motions in that higher frequency components are present. The peak ground accelerations transverse and along the fault are found to be of the same order of magnitude.