Probabilistic Tsunami Hazard Analysis Along Chinese Coast

In the past two centuries,the world witnesses 2500 tsunamis,95% of which are caused by earthquake and result in serious damage along coast area.Because of long coastline and geographical location,China have attacked by several tsunami,according to history record.With the development of economic,many metropolis occurred in southeast of China,which is characterized by dense population,dense capital and important infrastructure.The hazard of those area are more and more important,especially the extreme event in 2004 and 2011,which called up attention for tsunami among population.How the potentntial tsunami sources(PTSs)affect Chinese coastline and how to quantize it need study specially.More specific,how to consider tsunami hazard in coastal engineering,consider the effect of uncertainty of focal process,source parameter in probabilistic tsunami hazard anlysis,given those parameters make a difference on tsunami hazard curve.To solve those knot,we do some work relevanted as following:Firstly,determine the influence area of each PTS.Select the upper-limited magnitude as the max magnitude,fault parameter of PTS as the parameter of earthquake model.Determine the width,length and dislocation of rupture by empirical relationship.We employ COMCOT to simulate the generation and propagation of tsunami,according the max wave height,address the influence map of each local PTS.Secondly,for PTHA,the seismic activity parameters is must be known for each PTS.For local PTSs,the region of a single PTS is too small to collect aadequate data of historical earthquake event for analysis of seismicity.Here,we take advantage of Chinese national zonation map and take area as the only factor of seismic activity to calculate the seismic activity parameters of local PTSs.For regional PTS,because of the abundant historical earthquake record,we employ G-R relationship to determine the value of a and b,and then get the annual occurrence rate.We take consider of possibility of tsunamigenic earthquake by multipling it by ratio of tsunamigenic earthquake,which is proportion of tsunamigenic earthquake among earthquake according to historical earthquake event.Thirdly,probabilistic tsunami hazard analysis of southeast China.Six typical measured sites are selected to present six city located along coastline.According to PTSs and seismic activity parameters determined above,generate 200 earthquake samples by Monte Carlo,determine the width,length and dislocation of each rupture by empirical relationship.After simulate the tsunami with COMCOT,we match the distribution model of max wave height and get the risks of tsunami facing the coastline.By compare wave height and contribution of each potential source,we find the local source has more influence than manila potential.Finally,we propose a solution consider parameter uncertainty in PTHA.Because of the complexity of tsunami source and random of rupture,it is inevitable that there are some uncertainty involed in PTHA.In consideration of the effect of those uncertainty on hazard curve,we divide the uncertainty parameters in PTHA into aleatory uncertainty and epistemic uncertainty according to its nature,deal with epistemic uncertainty with logic-tree.After build the distribution model of aleatory uncertainty,discretize the value range with related probability,then handle it with event-tree.After harvest the event-tree,we can get 20%,and 80% fractile of tsunami hazard curve.take manila potential tsunami source as example,set slip,dip,area as uncertain parameter,calculating the tsunami hazard of Pearl River Estuary,and the result indicate that hazard curve are sensitivity to the change of those parameters.