Coda wave attenuation in Northern Aceh, Indonesia from a single station measurement: preliminary results

Abstract

Sumatra-Andaman subduction zone is one of the most active tectonic areas in the world. Understanding seismic risk in this region is important for hazard mitigation. One of the crustal physical properties is attenuation. Attenuation structure may affect the seismic propagation through the medium. It expresses the seismic wave amplitude decay when wave propagates through a medium. In this preliminary result, we report the seismic attenuation characteristics in Northern Aceh, Indonesia. We estimate coda waves attenuation from a single station from GE network. using a single back-scattering model. We analyze about 123 waveforms from local earthquakes (less than 3°) with magnitudes between 3 and 6 using a single back-scattering model. The depth of the events is selected to be shallower than 40 km depth. We estimate coda quality factor (Qc ) for each event at frequencies 1 – 8 Hz. The coda window is estimated from two times of S-wave arrival time with different window length ranging from 20 to 80 s. Reference coda quality factor (Q0 ) is selected at frequency of 1 Hz. We obtain that Q0 varies from 74.34 ± 10.04 to 160.2 ± 5.96 at 20 s and 80 s window lengths, respectively. The frequency dependence factor (η) decreases from 1.12 ± 0.06 to 1.05 ± 0.03 at 20 s and 80 s window length, respectively. An increase of Q0 with window length may suggest the depth dependent of seismic wave attenuation at reference frequency of 1 Hz. Low Q0 and high η are also consistent with this region’s high tectonic activity.