深厚软土非线性地震效应:震害启示、百年认知与未来挑战OA

Local site conditions,particularly those involving thick sedimentary layers that are suscepti-ble to the amplification effects,can significantly modify seismic ground motions,often exacerbating structural damage and posing catastrophic risks to major cities.To advance risk assessment and mitiga-tion for future mega-earthquakes,this paper presents a systematic and critical review of the global ob-servations and insights from the past century on nonlinear site effects in deep soft soil deposits.It fo-cuses on the evolution,current state,and persistent challenges in site response analysis methodolo-gies.First,drawing on macroseismic site effect phenomena and strong-motion records from regions such as the San Francisco Bay Area(1906 MW7.8 and 1989 MW6.9 earthquakes),the Mexico City Ba-sin(1985 MW8.1 and 2017 MW7.1 earthquakes),the Weihe Basin(2008 Wenchuan MS8.0 earthquake),and the Tokyo Bay Area(e.g.,1923 MW7.9 and 2011 MW9.1 earthquakes),we reveal characteristic features of nonlinear site amplification in deep alluvial plains and sedimentary basins.These include pronounced amplification of long-period ground motions from far-field large earthquakes,prolongation of strong shaking,site-structure double resonance effect,and basin-edge effects,among others.Next,we outline the development of site response analysis methods and corresponding software,from one-dimensional frequency-domain equivalent linear analysis to time-domain nonlinear methods(total stress and effective stress approaches),and further to complex two-and three-dimensional nonlinear wave propagation simulations.The theoretical principles,validation against downhole array record-ings,applicability,and limitations of these approaches are extensively discussed.Finally,considering potential extreme earthquake risks facing metropolitan regions in China′s alluvial plains composed of deep soft soil deposits(e.g.the Haihe Plain and Yangtze River Delta),we identify three fundamental issues:(1)constitutive models capable of capturing the strong nonlinear behavior of very deep soft soil deposits;(2)the construction of regional-scale numerical models that reasonably represent not only the inherent spatial variability of extremely deep,complex deposits,but also the associated parameter un-certainties;and(3)the development of efficient yet high-precision 2D and 3D nonlinear wave simula-tion methods.Addressing these challenges is crucial for deepening the fundamental understanding of site effects and establishing a robust scientific basis for enhancing urban seismic resilience against fu-ture mega-earthquakes.