Extracting ground motion characteristics of distant earthquakes for mitigating displacement-sensitive equipment

Abstract

Ground motions induced by strong, distant earthquakes may contain extremely long-period seismic waves that have a dominant period of up to 10 s. In general, these long-period seismic waves have small amplitudes and do not endanger the safety of building structures and civil infrastructures. However, they may bring unexpected shutdown of some vibration (displacement)-sensitive equipment (such as the wafer scanners in high-tech fabs), which can cause production loss. In this study, seismic waveforms collected from broadband seismometers distributed in Taiwan were used to investigate the ground motion characteristics of the collected distant earthquakes (with an epicenter distance of over 1000 km). The time-variant dominant frequency was extracted using moving window wavelet packet transform to monitor significant long-period seismic waves from the preevent data of each seismic event. The slope of the Arias intensity and the slope index of the recorded seismic waves were also developed to detect the potential accumulation of vibration energy increasing with respect to time and amplitude. The proposed index was used to detect the features of significant distant earthquakes, and it provides a mechanism to prevent unexpected shutdown of displacementsensitive equipment. Finally, the proposed approach is discussed in relation to the damage severity of high-tech fabs.

Novel prediction models of earthquake early warning for ground motion power in Taiwan

“…They also reported that the seismic waves that damage these scanners do not pose a threat to structural systems or cause human discomfort, which indicates that the PGA and PGV of these waves are not excessively high. Huang et al 11 . defined the slope index as the variation rate of the Arias intensity within a specific time window, which is also conceptually similar to ground motion power.…”

“…Studies have indicated that the power of seismic waves strongly correlates with the level of structural damage induced 8,9 and the shutdown of high-tech equipment during high-precision processes. 10,11 Zengin and Abrahamson 8,9 defined ground motion power as a function of the structural fundamental period. By performing nonlinear inelastic dynamic time history analyses of three-and nine-story frames, they reported that the power of ground motions strongly correlates with structural maximum inter-story drift.…”

“…Studies have indicated that the power of seismic waves strongly correlates with the level of structural damage induced 8,9 and the shutdown of high‐tech equipment during high‐precision processes 10,11 . Zengin and Abrahamson 8,9 defined ground motion power as a function of the structural fundamental period.…”

“…They also reported that the seismic waves that damage these scanners do not pose a threat to structural systems or cause human discomfort, which indicates that the PGA and PGV of these waves are not excessively high. Huang et al 11 defined the slope index as the variation rate of the Arias intensity within a specific time window, which is also conceptually similar to ground motion power. They reported that the slope index strongly correlates with the shutdown of displacement-sensitive equipment and that the ground motions induced by long-distance earthquakes, which have low PGA and PGV but high power, result in the shutdown of such equipment.…”