| 海底地震有限断层破裂模型对近场海啸数值预报的影响 |
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| 引用本文： | 王培涛,于福江,原野,闪迪,赵联大.海底地震有限断层破裂模型对近场海啸数值预报的影响[J].地球物理学报,2016,59(3):1030-1045. |
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| 作者姓名： | 王培涛 于福江 原野 闪迪 赵联大 |
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| 作者单位： | 1. 国家海洋环境预报中心, 北京 100081;2. 国家海洋局海啸预警中心, 北京 100081;3. 国家海洋环境预报中心海洋灾害预报技术研究国家海洋局重点实验室, 北京 100081 |
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| 基金项目： | 海洋公益性行业科研专项项目(201205034,201305031,201405026),国家科技支撑计划课题(2013BAB04B02)资助. |
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| 摘 要： | 快速准确的海啸源模型是近场海啸精确预警的关键.尽管目前还没有办法直接对其进行正演定量计算,但是可以通过多源地震、海啸观测数据进行反演或联合反演推算.不同的海啸源可能导致不同的预警结论,了解不同类型海啸源适用性、评估海啸源特征差异对近场海啸的影响,无论对于海啸预警还是海啸模拟研究尤为重要.本文评估分析了6种不同同震断层模型对2011年3月11日日本东北地震海啸近场数值预报的影响,重点对比分析了有限断层模型与均一滑动场模型对近场海啸产生、传播、淹没特征的影响及各自的误差.研究表明:近场海啸波能量分布主要取决于海啸源分布特征,特别是走向角的差异对海啸能量分布影响较大;有限断层模型对海啸灾害最为严重的39°N以南沿岸地区的最大海啸爬坡高度明显优于均一滑动场模型结果;综合对比DART浮标、GPS浮标及近岸潮位站共32个站次的海啸波幅序列结果发现有限断层模型整体平均绝对/相对误差比均一滑动场模型平均误差要低,其中Fujii海啸源的平均绝对/相对误差最小,分别是0.56m和26.71%.UCSB海啸源的平均绝对/相对误差次之.3个均一滑动场模型中USGSCMT海啸源模拟精度最高.相对于深海、浅海观测站,有限断层模型比均一滑动场模型对近岸观测站计算精度更高.海啸源误差具有显著的方向性,可能与反演所采用的波形数据的代表性有关;谱分析结果表明Fujii海啸源对在12至60min主频波谱的模拟要优于UCSB海啸源.海啸源中很难真实反映海底地震破裂过程,然而通过联合反演海啸波形数据推算海啸源的方法可以快速确定海啸源,并且最大限度的降低地震破裂过程与海啸产生的不确定性带来的误差.
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| 关 键 词： | 海底地震 有限断层破裂模型 近场海啸 谱分析 Dart浮标 数值预报 联合反演 |
| 收稿时间： | 2014-11-20 |
Effects of finite fault rupture models of submarine earthquakes on numerical forecasting of near-field tsunami |
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| WANG Pei-Tao,YU Fu-Jiang,YUAN Ye,SHAN Di,ZHAO Lian-Da.Effects of finite fault rupture models of submarine earthquakes on numerical forecasting of near-field tsunami[J].Chinese Journal of Geophysics,2016,59(3):1030-1045. |
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| Authors: | WANG Pei-Tao YU Fu-Jiang YUAN Ye SHAN Di ZHAO Lian-Da |
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| Institution: | 1. National Marine Environment Forecasting Center, Beijing 100081, China;2. Tsunami Warning Center, State Oceanic Administration, Beijing 100081, China;3. Key Laboratory of Research on Marine Hazards Forecasting, National Marine Environmental Forecasting Center, State Oceanic Administration, Beijing 100081, China |
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| Abstract: | Fast and correctly characterizing tsunami source is crucial to accurate early warning of near-field tsunami. Although there is no way to implement forward quantitative calculation directly, a tsunami source can be inverted using real-time tsunami or seismic waveform records which are detected by Dart buoys, GPS buoys, tidal gauges and seismometers, respectively, and also by joint inversion using different sources data. Because different typical tsunami source models may come to different conclusions, it is important for tsunami early warning and tsunami research to learn about the applicability of different tsunami sources and assess the impacts of tsunami source characteristics differences of near-field tsunami. This study analyzed the effects of six different coseismic fault models on near-field numerical forecasting to the tsunami triggered by the March 11, 2011 Tohoku-oki earthquake. A variable nested algorithm was used to increase spatial resolution in the target region. The finest bathymetric grid resolution was 3 arcsec(approx.90m). The present work focused on assessing the performance of the finite fault model and uniform slip model in near-field tsunami generation, propagation, inundation and their respective characteristic errors by comparing the simulated data with the measured data. From observed data of the Deep-Ocean Assessment and Reporting for Tsunamis(DART) network, Japan GPS buoys, we selected tide gauges along the coastline of Japan and post-even survey. The measured data were compared with forecasts to assess the sensitivity of the six different sources using error analysis. The results show that the characteristics of the energy distribution of near-field tsunami is much dependent on tsunami source geometry. In particular, the strike angle and slip are the most sensitive parameters for the energy distribution of near-field tsunami. Comparison indicates that finite fault models are more reasonable than uniform slip models in fitting maximum tsunami run-up height south of 39°N coastal areas, where occurred the most serious tsunami disaster. A total of 32 sea level monitors including Dart buoys, GPS buoys and tide gauges were used to verify the errors of model data. The simulation results of finite fault models fit the observed records better than uniform slip models as a whole. They have the relatively lower mean absolute/relative error. Fujii's source has the lowest absolute/relative error(0.56 m and 26.71%). UCSB tsunami source also has a better accuracy. At the same time USGSCMT source has the highest precision among three uniform slip models. This paper also suggests that using finite fault models can attain obviously higher precision at tide gauges than uniform slip models with respect to DART buoys and GPS buoys stations, and the errors of tsunami sources have significant orientations. The comparison of tsunami wave spectra was carried out with Fujii's source and UCSB source simulated data. Modeling results from Fujii's source show the better agreement with the spectral energy at wave periods between 12 and 60min than UCSB source. Comparison of tsunami sources inferred from different indirect methods shows the crucial importance of tsunami waveforms for initial seafloor deformation inversion. The joint inversion of tsunami waveform data especially using the deep-ocean tsunami signal can determine the tsunami source quickly and reduce the errors caused by the uncertainty of earthquake rupture processes, which can aid understanding of tsunami generation from earthquakes and nonseismic processes. |
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| Keywords: | Submarine earthquake Finite fault rupture models Near-field tsunami Spectrum analysis Dart buoys Numerical forecasting Joint inversion |
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