Neo-deterministic Seismic Hazard Assessment(NDSHA) For The China Seismic Experimental Site(CSES)

In the Spring of 2021,approved by Standing Committee of the National People’s Congress of China,the China Seismic Experimental Site（CSES）was enlisted as a key state scientific infrastructure in the 14^th national five-year plan during 2021 to 2025 of economic,social development and the long-term vision of 2035.Such a governmental decision represents a major step in promoting earthquake science in China.In the seismically active southwestern China many devastating earthquakes,e.g.,the Wenchuan(2008,May 12^th,Ms8.0)and Lushan(2013,April 20^th,Ms7.0)earthquake,inflicted heavy casualties and property losses.Facing such a severe threat,it is crucial and urgent to conduct reliable seismic hazard estimation considering,in a critical perspective,all the available probabilistic and deterministic approaches for the estimation of seismic hazard and risk.It is known that discussion about Pros and Cons between deterministic and probabilistic approach has been going on for many years.With this background,the introduction of Neo-deterministic Seismic Hazard Assessment（NDSHA）approach in the CSES plan will significantly deepen the understanding of seismic hazard in this area in a physics-based deterministic perspective for the first time.In the thesis,a first-order seismic zoning based on NDSHA in the study area delimited by 94°～108°E and 19°～-35°N,containing the SouthEast margin of the Tibetan Plateau and the Sichuan-Yunnan region,has been performed.The seismic hazard is expressed by maps of peak ground displacement（PGD）,peak ground velocity（PGV）and design ground acceleration（DGA）values,extracted from synthetic seismograms computed at a regional scale and mapped on a regular grid of 0.2°×0.2°over the study area.For the computation of synthetic seismograms,all the available geophysical-geological-tectonic information,including historical and instrumental earthquake catalogues,seismogenic zones,seismogenic nodes,focal mechanisms,and geophysical structural models were collected and refined.These firstorder NDSHA zoning findings may serve as a knowledge basis to support both largeto mid-range preparedness actions and（multi-scenario）site specific studies.The thesis also presents the synergy of NDSHA findings with the Chinese scientific environment,e.g.,Annual Consultation on the Likelihood of Earthquake and Earthquake Early Warning System（EEWS）.Such innovative combination between NDSHA,Annual Consultation and（on-site）EEWS may improve the information service provided to society and decision-makers for earthquake emergency response and then contribute to the reduction of seismic disaster risk.In addition,the（frontdetection）EEWS empowered by real-time NDSHA,and the modification to GreatEarthquake-Prone-Areas input to NDSHA computation is also discussed.For a basic understanding to differences among various seismic hazard assessment（SHA）approaches,the history and developments of them are sorted out in Chapter Ⅰ.Chapter Ⅱ describes the current state of seismic hazard assessment and earthquake forecasting in China,then supplies an overview of the pioneering applications of NDSHA in North China since the start of 20th century.At the end of the chapter the research area,i.e.,CSES,is briefly described.Chapter Ⅲ describes the main steps in the of NDSHA evaluation,while ChapterⅣ deals with the data used and the preprocessing for the computation of NDSHA in the CSES area.Chapter Ⅴ contains the computational results of NDSHA applied in CSES,including design ground acceleration（DGA,i.e.the maximum horizontal acceleration）,peak ground velocity（PGV）and peak ground displacement（PGD）.Chapter Ⅵ deals with the combination of NDSHA and Annual Consultation on the Likelihood of Earthquakes at one-year scale.Chapter Ⅶ deals with the network-based on-site EEWS,where the blind zone is one of the challenges affecting its effectiveness.Chapter Ⅷ proposes a possible combination of front-detection EEWS and reliable seismic hazard assessment.Chapter IX describes a possible modification to the shape of M～8.2 seismogenic nodes,i.e.,Great-Earthquake-Prone Areas（GEPAs）,based on tectonic blocks,seismogenic zones and 150 km radius circular GEPAs.Chapter X summarises the main content in the whole thesis,and prospects the work in the future.This chapter consists of four branches:（1）the first-order Neodeterministic Seismic Hazard Assessment（NDSHA）in the CSES area;（2）NDSHA for the improvement of Annual Consultation on the Likelihood of Earthquakes;（3）On-site and front-detection EEWS empowered by NDSHA;（4）Finite rupture attributes associated with the Great-Earthquake-Prone-Areas（GEPAs）.For the seismically active Sichuan and Yunnan Provinces,these computed maps,the expansion and exploration to comprehensively consider the Chinese reality（e.g.Annual Consultation and EEWS）,and the modification to the shape of M≥8.2 seismogenic nodes will provide a new reference choice for structural engineers and decision makers,and further promote the development and application of NDSHA method in the reduction of seismic risks.