A microtremor study to reveal the dynamic response of earth fissure site: the case study in Fenwei Basins, China

摘要

While earth fissures are fairly common and potentially hazardous, these phenomena have been largely ignored, especially with respect to how the presence of earth fissures could impact the dynamic site response of a given region. To determine the dynamic response characteristics of sites with earth fissures, systematic microtremor testing was conducted over 31 representative earth fissures in Fenwei Basin. Three metrics (Fourier spectrum (HVSR), acceleration response, and Arias intensity) were employed to evaluate changes in the spectral characteristics of the microtremor data recorded at these earth fissure sites, as well as to determine the amplification effect and its attenuation rules. The results show that, by reason of the existence of these earth fissures, the peak amplitude for the three metrics in the spectral data reach the extreme values at the fissures and are particularly prominent on the hanging wall. The amplification effect decreases and eventually disappears with increasing distance from the fissure. The dynamic amplification factor can at least exceed values of 2 near the fissure. The amplification factor typically drops to 1.5 at distances of similar to 7 m from the earth fissure and decays to a stable value at about 23 m from the earth fissure. The empirical equations describing the dynamic response of different basins and various earth fissures are also determined.