Tem po ral b - Value Vari a tions through out a Seis mic Fault ing Pro cess : The 2008 Taoyuan Earth quake in Taiwan

Tem po ral b-value vari a tions have been com pletely ob tained for the seis mic fault ing pro cess of the 4 March 2008 Taoyuan earth quake (ML = 5.2), south ern Tai wan. In ad di tion to trig ger ing sev eral hun dred after shocks, the mainshock was pre ceded by two groups of foreshocks (64 events) that clus tered along the nar row ma jor fault zone. A high b-value of ~1.25, es ti mated from the foreshock se ries, rep re sent ing fault growth, was sig nif i cantly larger than the b-val ues of 0.80 and 0.81, ob tained re spec tively from after shocks and back ground seis mic ity. Also there were some pre-shocks (i.e., mi cro-earth quakes) that oc curred one month be fore the earth quake se quence, with an ex tremely high b-value of ~2.1. This num ber might suc cess fully in di cate pre-nu cle ation seis mic fea tures in the vi cin ity of the fault zone. These seis mic char ac ter is tics are fun da men tally very sim i lar to gen eral fea tures such as frac ture nu cle ation and growth ob served in rock sam ples un der con trolled stress in lab o ra tory ex per i ments, and thus ought to be considered to improve our understanding of crustal fault growth.