A Study of the Unified Scaling Law of Earthquakes in the Taiwan Region

Abstract

The unified scaling law (also called the BCDS model), merges: (1) Omori's Law, (2) Gutenberg-Richter's law, and (3) the geometrical fractal distribution of epicenters, all of which, in combination, investigate the occurrence of earthquakes from a spatial-temporal perspective. This study plans to verify important questions arising from the definition of the BCDS model by doing three experiments. Firstly, we examine the feasibility of applying this model to Taiwan using different cell sizes and cut-off magnitudes. Secondly, we ascertain the difference between aftershocks and main shocks in a unified scaling law by comparing earthquake time sequences with declustered ones. Thirdly, we investigate the differences among scaling relationships obtained from various geological settings in Taiwan.

Our results show that no matter how cell size and cut-off magnitude change, they produce a very similar pattern symbolizing the scaling law. Using a Z-map, after declustering, the constant part, which is an apparent indicator of the characteristics of aftershocks, disappears, and the slope of the fast decaying part, which corresponds to the main shock, remains almost the same. In addition, scaling laws obtained from four different sub-regions in Taiwan, although slightly different to each other, all show to be of a similar scaling law.

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