Time-dependent earthquake hazard evaluation in seismogenic systems using mixed Markov Chains: An application to the Japan area
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2006
Received: 18 October 2005
Accepted: 20 April 2006
Published: 16 September 2006
A previous work introduced a new method for seismic hazard evaluation in a system (a geographic area with distinct, but related seismogenic regions) based on modeling the transition probabilities of states (patterns of presence or absence of seismicity, with magnitude greater or equal to a threshold magnitude Mr, in the regions of the system, during a time interval Δt) as a Markov chain. Application of this direct method to the Japan area gave very good results. Given that the most important limitation of the direct method is the relative scarcity of large magnitude events, we decided to explore the possibility that seismicity with magnitude M ≥ M r m contains information about the future occurrence of earthquakes with MM r m > M r m . This mixed Markov chain method estimates the probabilities of occurrence of a system state for M ≥ M r M on the basis of the observed state for M ≥ M r m in the previous Δt. Application of the mixed method to the area of Japan gives better hazard estimations than the direct method; in particular for large earthquakes. As part of this study, the problem of performance evaluation of hazard estimation methods is addressed, leading to the use of grading functions.