Identification of ground motion features for high-tech facility under far field seismic waves using wavelet packet transform

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 displacement-sensitive equipment. Finally, the proposed approach is discussed in relation to the damage severity of high-tech fabs.

Download Full-text

Study on Far-Field Ground Motion Characteristics

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.438-439.1471 ◽

2013 ◽

Vol 438-439 ◽

pp. 1471-1473

Author(s):

Gong Lian Chen ◽

Wen Zheng Lu ◽

Lei Wang ◽

Qi Wu

Keyword(s):

Ground Motion ◽

Seismic Design ◽

Seismic Waves ◽

Response Spectrum ◽

Engineering Application ◽

Seismic Attenuation ◽

Far Field ◽

Propagation Process ◽

Ground Acceleration ◽

Motion Characteristics

In order to study the far-field ground motion characteristics and the attenuation of seismic waves, the peak ground acceleration (velocity, displacement), time of duration and response spectrum of the seismic waves were analyzed in this paper. Through the investigation of earthquake wave propagation process, the seismic attenuation low was analyzed. This study can provide technical support for the seismic design of long period structures and related engineering application.

Download Full-text

Seismic response analysis of loess site under far-field bedrock ground motion of the Wenchuan earthquake

PLoS ONE ◽

10.1371/journal.pone.0254871 ◽

2021 ◽

Vol 16 (7) ◽

pp. e0254871

Author(s):

Tuo Chen

Keyword(s):

Ground Motion ◽

Seismic Waves ◽

Linear Method ◽

Soil Layer ◽

Resonance Phenomenon ◽

Amplification Coefficient ◽

Response Analysis ◽

Topographic Effects ◽

Far Field ◽

Short Period

In this paper, considering the far-field seismic input, an accelerogram recorded in the bedrock at Wuquan Mountain in Lanzhou city during the 2008 Wenchuan Ms8.0 earthquake was selected, and numerical dynamic analyses were conducted. The one-dimensional equivalent linear method was implemented to estimate the ground motion effects in the loess regions. Thereafter, slope topographic effects on ground motion were studied by applying the dynamic finite-element method. The results revealed the relationship between the PGA amplification coefficients and the soil layer thickness, which confirmed that the dynamic response of the sites had obvious nonlinear characteristics. The results also showed that there was an obvious difference in the dynamic magnification factor between the short-period and long-period structures. Moreover, it was found that the amplification coefficient of the observation point at the free surface was greater than the point inside the soil at the same depth, which mainly occurred in the upper slope. Through this study, the quantitative assessment of ground motion effects in loess regions can be approximately estimated, and the amplification mechanism of the far-field ground motion mechanism can be further explained. In addition to the refraction and reflection theory of seismic waves, the resonance phenomenon may help explain the slope topographic effect through spectrum analysis.

Download Full-text