Abstract
Microzonation is one of the essential tools in seismology to mitigate earthquake damage by estimating the near-surface velocity structure and developing land usage plans and intelligent building design. The number of microzonation studies increased in the last few years as induced seismicity becomes more relevant, even in low-risk areas. While of vital importance, especially in densely populated cities, most of the traditional techniques suffer from different shortcomings. The microzonation technique presented here tries to reduce the existing ambiguity of the inversion results by the combination of single-station six-component (6C) measurements, including three translational and three rotational motions, and more traditional H/V techniques. By applying this new technique to a microzonation study in the downtown area of Munich (Germany) using an iXblue blueSeis-3A rotational motion sensor together with a Nanometrics Trillium Compact seismometer, we were able to estimate Love and Rayleigh wave dispersion curves. These curves together with H/V spectral ratios are then inverted to obtain P- and S-wave velocity profiles of the upper 100 m. In addition, there is a good correlation between the estimated velocity models and borehole-derived lithology, indicating the potential of this single-station microzonation approach.
Highlights
In seismic microzonation, the velocity structure of the upper few 100 m is estimated in order to characterize the local earthquake shaking characteristics
The objective of this study was to test a new singlestation technique for seismic microzonation in order to improve the resolution of the resulting 1D velocity models
The single-station approach using a Trillium Compact 120s seismometer and the blueSeis-3A rotational sensor makes measurements very simple in terms of logistics compared with an array setup, especially when working in an urban area
Summary
The velocity structure of the upper few 100 m is estimated in order to characterize the local earthquake shaking characteristics. The single-station H/V method is commonly applied in microzonation studies, but its theoretical foundation is still not completely understood and the results highly depend on the quality of the noise (e.g., Malischewsky and Scherbaum (2004)). Wassermann et al (2016) demonstrated that a single-station six-component approach, combining rotational motion measurements (which are related to the gradient of a seismic wave field) with traditional translational recordings (i.e., recordings of ground velocity), may give comparable results to array techniques for the estimation of the 1D local velocity structure and the dominant direction of the incident wave field
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