考虑场地非线性的宽频地震动数值模拟方法

BROADBAND GROUND MOTION SIMULATION METHOD CONSIDERING NONLINEAR SITEEFFECTS

许可

11849248

硕士

力学

张伟

2020-05-30

2020-05-30

哈尔滨工业大学

深圳

数值模拟是强地面运动研究的常用手段之一，对于强震记录不足地区的地震动危险性评估更具有重要意义，但当前强地面运动数值模拟仍面临一些方面的挑 战，包括高频带模拟和场地效应评估等。一方面，在抗震工程设计中，0.1Hz 到 20Hz 的宽频带地震动响应均具有重要意义，但由于计算能力限制及小尺度震源、 介质信息难以获取，其中的高频部分难以通过确定性数值模拟进行计算。因此低频采用确定性方法、高频采用其他方法的混合模拟是当前弥补这一缺陷的常见手段。另一方面，在全球很多地区，沉积盆地或人工填土中的场地效应也对强地面运动有很大影响，但由于近地表场地介质具有低波阻抗和非线性等性质，不便直接包含在基于物理的数值模拟中，而是主要采用先模拟后校正的方法。由于校正过程常需利用闭源商业软件，实现过程有一定限制，因此在宽频地震动模拟基础上加入场地校正模块，形成适用于我国地震危险性评估的完整模拟系统，是一种合理的优化方案。在本研究中，我们发展了一种新的程序，利用与有限断层高频随机方法和一 维频域等效线性场地校正方法的耦合, 将同位网格有限差分方法（CG-FDM）拓展 至含场地非线性的地震动宽频一体化模拟。此程序所需输入包括震源机制与时间破裂模型、区域地壳速度结构模型、近地表各点土层钻孔数据及其构造的土层骨干曲线与滞回曲线一维模型等，并可直接模拟得到包含场地效应的宽频合成地震动反应时间过程和频谱结果。此外，本研究中对高频随机模拟模块进行了有限断层拓展和到时修正，并分别对高频与场地模块进行了单独检验与分析，在保证了结果可靠性的同时，使其能够用于大断层强震、包含复杂介质条件及起伏地形的区域尺度强地面运动模拟。 本文利用上述方法和程序对2008年汶川地震的四川地区强地面运动进行了模 拟实验，其所需的震源、介质、土层模型均由前人的研究结果得到；与仅采用确定性模拟方法相比，其模拟得到的合成地震动与实际观测数据呈现出更好的拟合效果。由于此方法将模拟所需的各部分计算模块化并有机结合，可以同时实现强地面运动模拟的各项目标，期待可以在地震危险性评估和抗震工程中得到更广泛的应用。

Numericalsimulationisoneofthemostimportanttoolintheresearchonearthquake groundmotions,especiallyinseismichazardassessmentforareaslackexistingrecordings. However,severalaspectsstillneedfurtherconsideration,includingbroadbandsimulation and site effects analysis. On the one hand, broadband response of 0.1˜20Hz are all vital information for seismic design, but there are difficulties in applying small-scale source andmodeldataasinputsforsimulationinhigh-frequencyband. Hybridmethods,which combine low-frequency deterministic methods and various high-frequency methods, are widely used to make up for this defect and give broadband simulation results. On the other hand, the influence of site effects on strong ground motion is of a great concern in many areas. But due to low-velocity and non-linearity, the non-linear site effect is usually not included in the physics-based numerical simulations (PBSs), instead is generally implemented by a post-correction approach. Since the correction process is often completed via closed-source commercial softwares, which may introduce some restrictionsinuse,it’saneffectiveimprovementtoincorporatesite-analysismodulebased on broad-band ground motion simulation, and generate a complete modeling system for seismichazardassessmentinChina. Wedevelopedanewprograminthisstudy,toextendtheCollocatedGridFiniteDifferenceMethod(CG-FDM)intocombinedbroadbandgroundmotionsimulationconsidering nonlinearsiteeffects,bycouplingfinite-faulthigh-frequencystochasticsimulationmethod and 1D frquency-domain equivalent-linear site effect analysis method. In the program, kinematicseismicsource-rupturemodel,regionalvelocity-structuremodel,andnonlinear soil properties to depict backbone and hysteretic curves for layered models at discrete grid-pointsareneededasinputs,andthusthetimehistoryandfrequencyspectraaregiven asresultsforbroadbandsyntheticseismicresponseconsideringsite-effects. Furthermore, thehigh-frequencystochasticmethodismodifiedinthisstudytoincludefinite-faultmodels and arrival time modifications, and the high-frequency and site-analysis modules are tested and analyzed seperately, after which the whole modeling system is guaranteed to be capable in regional strong ground motion simulation given large-fault earthquakes, complexmediaandtopography. We apply above methodology and program on strong ground motion simulation of -IIthe2008Mw7.9WenchuanearthquakewithinSichuanarea,wherethenecessarysource, medium, and soil data of the surrounding region have been obtained by previous researchers. Thesyntheticseismicresponsefitstheobservedseismicrecordingsbetterthan deterministic methods only. Since all three computation modules needed in simulation are combined organically, it could achieve all objectives in strong ground motion simulation at one run, and is expected to be used more widely in seismic hazard analysis and earthquakeengineering.

有限差分 等效线性法 宽频带 场地效应 强地面运动

Finite-difference Equivalent-linear Broadband Site Effect Strong Ground Motion

中文

联合培养

南方科技大学

许可. 考虑场地非线性的宽频地震动数值模拟方法[D]. 深圳. 哈尔滨工业大学,2020.