Fluctuation Analyses of M ≥ 3 Earthquake Sequences in The Taipei Metropolitan Area

The M ≥ 3 earthquakes which occurred in the Taipei Metropolitan Area from 1973 through 2010 are used to study the memory effect of earthquake sequences in the area by applying a fluctuation analysis technique in the natural time domain. The earthquakes can be divided into two groups: the first for shallow events with focal depths ranging 0 - 40 km and the second with focal depths deeper than 60 km. For both shallow and deep earthquakes, three magnitude ranges, i.e., M ≥ 3, M ≥ 3.5, and M ≥ 4, are taken into account. The calculations are also made for the events in a smaller area. Calculated results show that the exponents of the scaling law of fluctuation versus window length for all earthquakes sequences in consideration are not larger than 0.5, thus suggesting that the M ≥ 3 and M ≥ 3.5 earthquakes in the TMA are short-term corrected. On the other hand, the M ≥ 4 earthquakes are weakly corrected.