Seismicity Pattern Changes Prior to Large Earthquakes -An Approach of the RTL Algorithm

                                                 Yi-Xuan Wu

                  Institute of Geophysics, NationalCentralUniversity, Chungli, Taiwan 320.

                                           ABSTRACT

          A statistical method, which is called the Region-Time-Length (RTL) algorithm and
        takes into account information such as magnitude, occurrence time and place of
        earthquakes, was applied to earthquake data to investigate seismicity pattern changes
        prior to large earthquakes. The results indicated that seismic quiescence anomalies
        generally started a few years before the occurrence of the earthquakes and lasted from 1
        to 2.5 years. The duration of the subsequent stage of seismic activation generally lasted
        several months. An earthquake is most likely to occur once the relevant source region has
        passed through the quiescence and activation stages. Close investigation of possible
        artifacts due to the selection of model parameters and the changes of seismological
        networks are important in identifying real seismicity changes from man-made ones.It
        indicated that an increased RTL parameter would be a new potentiallyuseful index for
        the risk alarm of earthquake swarms.

                                           REFERENCE

        Huang, Q., Sobolev, G.A. & Nagao, T., 2001. Characteristics of the seismic quiescence 
        and activation patterns before the M = 7.2 Kobe earthquake, January 17, 1995, 
        Tectonophysics, 337, 99–116.
                                            (Abstract)(Full text)

        Huang, Q., A. O. O˙˙ncel and G. A. Sobolev, 2002: Precursory seismicity changes 
        associated with the Mw = 7 4 . 1999 August 17 Izmit (Turkey) earthquake. Geophys. 
        J. Int., 151, 235-242.
                                            (Abstract)(Full text)

        Di Giovambattista, R., and Y. S. Tyupkin. Spatial and temporal distribution of seismicity 
        before the Umbria-Marche September 26, 1997 earthquakes. J. of Seismology., 4, 589–598
                                            (Abstract)(Full text)

        Huang, Q., Seismicity Pattern Changes Prior to Large Earthquakes -An Approach of the RTL 
        Algorithm. TAO, 15, No. 3, 469-491.
                                            (Abstract)(Full text)