On 16 September, 1972 at 04 15 09.8 UT an earthquake of magnitude ML 5.0 occurred in southeast Papua within about 20 km of a proposed dam site on the Musa River. The earthquake triggered two accelerographs, Musa A and Musa B, one at the crest and one at the base of the dam site. The peak ground accelerations recorded by the accelerographs were 1.85 m/s2 and 0.39 m/s2 respectively; the peak ground velocities were 87 mm/s and 2.0 mm/s; and the corresponding mean periods of the ground motion were about 0.23 and 0.04 s. The difference in the nature of the accelerograms is attributed to
the difference in the geological and topographical settings of the accelerograph sites. The upper site has an elevation of 406 m and consists of about 60 m of weathered sediments overlying fresh ultramafics. The lower site has an elevation of 112 m and consists of an outcrop of the ultramafic complex.