Seiche from Lakes

Minor seiches were also noted by residents at Naujan and Baruyan lakes. In Lake Naujan, people living nearshore at Bamban, Muntilago, awakened by the strong ground shaking, were able to observe half-meter oscillations of the lake. They also noticed sudden murkiness of the lake water probably as a result of lake bottom agitation. It took days before the water became clear again. No damage was attributed to seiche since the lake water oscillated with a wave height of less then a meter.

Lake Baruyan was severely shaken and the margins of the lake were lowered as an effect of the vertical movement along N-S trending sub-parallel faults. Fisherman who were in the lake during the earthquake noticed a considerable lowering of the lake water. This was attributed to the movement of the lake water towards the sea (northward) immediately after the earthquake. A few minutes later, a big volume of wave from the sea entered the lake. Most of the water stayed in the lake and did not retreat back to the sea. The volume of water was accommodated in the lake as a result of the downthrown movement of lake bed due to faulting. Consequently, local residents noticed a significant deepening of the lake level.

A power barge measuring 19m x 32m x 10m which was originally anchored at the mouth of Baruyan River was transported upstream for about 2 kilometers and then stranded at the entrance of the lake due to shallow water (Fig. 28). Since the wave that entered Baruyan Lake was not coupled with big run-down, the barge just stayed in place at the entrance of the lake.