Application of Discrimination Filter Based on the Polarization to the Surface Wave Records

Nilgun Sayil

Department of Geophysics, Engineering Faculty, Karadeniz Technical University, Trabzon, Turkey.

DOI: 10.4236/oalib.1100724                

Abstract

As well known, each type of seismic waves has a specific particle motion. The basic surface waves Love and Rayleigh show the particle motions polarized linearly in the transversal-horizontal plane and elliptically in the vertical-radial plane, respectively. Like in the body waves, polarization properties can be used to design the surface wave discrimination filter. The process consists of weighting the amplitudes of vertical (Z), radial (R) and tangential (T) components of the ground motion at each frequency according to the particle motion. The weighting process is applied to entire length of each component for selected window length and moving interval, but weights are not applied to the original phase values. The weighted parts for each window are transformed to the time domain and filtered signals are obtained as the arithmetic average of values of the overlapping points. The method has been applied to the broad-band digital three-component records at stations having about 10° epicenter distances of Bogazici University Kandilli Observatory and Earthquake Research Institute (KOERI) of Erzurum earthquakes and noticed that the window length and moving interval in proportion to epicenter distance affect the results on a large scale. For the cases in which the best results are obtained, it has been determined that the ratio between the window length and moving interval for increased epicenter distances are 3.95, 4.5 and 4.8, respectively.

Keywords

Discrimination Filter, Polarization Properties, Surface Wave

Conflicts of Interest

The authors declare no conflicts of interest.

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