OSMS 93-10

by CSMIP Staff

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Low-level accelerograms were recorded on the temporary SMIP instrumentation in the South Tower of the Golden Gate Bridge from a small, distant earthquake. The ML 5.3 earthquake occurred near Gilroy, approximately 130 km away. The locations of the 8 sensors in the east leg of the South Tower of the bridge are shown in Figure 1. Three sensors are located at the base level, three at the roadway level, and two sensors are at the top level of the South Tower. The orientation of the horizontal sensors is given on the data plots as 180° (parallel to the bridge, nominally South (S)) and 90° (transverse to the bridge, nominally East (E)). The temporary instrumentation system include two 12-bit synchronized digital recorders.

The peak acceleration, velocity and displacement on the bridge are 0.02 g, 1 cm/sec and 0.07 cm, respectively. This motion was recorded on channel 8, located at the top level, in the direction transverse to the bridge.