On the correlations between the largest foreshocks and mainshocks of earthquake sequences in Taiwan

We collected a data set of mainshocks and their respective largest foreshocks of 38 earthquake sequences in Taiwan. The plot of local magnitude, M-L, of a mainshock (denoted by M-Lm) versus M-L of its largest foreshock (denoted by M-Lf) shows an increase in M-Lm with M-Lf. This indicates that for Taiwan's earthquakes the bigger the largest foreshock is, the larger the mainshock is. The plot of the epicentral distance, ? (in km), from the largest foreshock to the mainshock versus ML of the mainshock exhibits a weak increase in ? with M-Lm as ?<10 km. The plot of the focal depth of the largest foreshock and that of the mainshock shows a linear increase in the former along with the latter for most event-pairs. Let T be the interval between the occurrence time of the largest foreshock and the mainshock. The plot of T versus M-Lm exhibits that the mainshock will occur within 5 days, with the highest probability of 1 day, after the occurrence of the largest foreshock. Let H be the hypocentral distance between the largest foreshock and the mainshock. The plot of T versus H reveals a slight increase in T with H when T>1 day.

Automated summary

The data set of earthquake sequences in Taiwan shows that the larger the largest foreshock, the larger the mainshock. The distance from the largest foreshock to the mainshock slightly increases when the mainshock's magnitude is less than 10 km. The focal depth of the largest foreshock and the mainshock linearly increase for most event-pairs. The mainshock usually occurs within 5 days, with the highest probability of 1 day, after the largest foreshock. When the time interval exceeds 1 day, it slightly increases with the hypocentral distance.