Microseismic Wave Measurements to Detect Landslides in Bengkulu Shore with Attenuation Coefficient and Shear Strain Indicator

Abstract

<p>It has been detected that the condition of landslides that occurred in Bengkulu Shore can change the position of the shoreline. This research aimed to: (1) calculate of shear strain (γ) and attenuation coefficient (ά) value  based on microseismic data in coastal areas that experienced landslides; (2) determine the correlation between levels of landslides with  shear strain  and attenuation coefficient value (3) determine the correlation between the shear strain and attenuation coefficient value. Microseismic data were processed and analyzed quantitatively using the Horizontal to Vertical Spectral Ratio method (HVSR) to obtain the ground vibrations resonance frequency (<em>f<sub>o</sub></em>) and amplification factor (<em>A</em>). Shear strain value was calculated from the of <em>f<sub>o</sub></em>, <em>A</em> and Peak Ground Acceleration (<em>α<sub>max</sub></em>) value. Peak Ground Acceleration value was calculated based on 100-year period of recorded earthquake data.  Attenuation coefficient was calculated based on the equation (2). The results of study showed that the value of shear strain in the coastal areas varied from 1.0 × 10<sup>-4</sup> to 3.6 × 10<sup>-3</sup>,  in accordance with the conditions of landslides. The attenuation coefficient value varied from 0.005 to 0.020.  Level of landslides that occurred varied from moderate, to very severe. There was a tendency that the more severe the landslide level,  the greater the shear strain and attenuation coefficient value were.</p>