Waveform Modeling of Earthquake Data for Delineating the Sedimentary Structure of the Anchorage Basin, Alaska

Abstract eng:
The paper presents waveform inversion technique using the local earthquake data to estimate the crustal structure of the Anchorage basin, Alaska. Three component recorded data of an earthquake (ML= 4.8) from 26 strong motion station sites in Anchorage area are used for this purpose. The technique uses parallelized reflectivity method to compute synthetic seismograms of SH-, SV-, and P- wave motions and implements global optimization technique based on simulated annealing inversion to fit the observed waveform data with the computed seismograms. The inversion searches for optimal values of four model parameters namely the layer thickness, P-wave velocity, P to Swave velocity ratio and density at each site. The inversion shows that the crustal thickness of the Anchorage basin is around 40 km with P- and S-wave velocity at the bottom of the crust is around 6.4 km/s and 3.8 km/s, respectively. It is noticed that the observed ground motions of the Anchorage basin are strongly affected by the S-wave velocities of the shallow (< 0.1 km) sediments. The P-wave amplification due to the basin sediments is not significant. The presence of low S-wave velocity zones primarily responsible for the observed variations of the ground motions characteristics within the Anchorage basin. The P-to-S-wave velocity ratio varies from 10.0 to 2.0 for the shallower parts of the basin and remains around 1.78 in the deeper parts of the basin.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket