RAPID TSUNAMI MODELS AND EARTHQUAKE SOURCE PARAMETERS: FAR-FIELD AND LOCAL APPLICATIONS
RAPID TSUNAMI MODELS AND EARTHQUAKE SOURCE PARAMETERS: FAR-FIELD AND LOCAL APPLICATIONS
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快速海啸模型和震源参数：远场和本地应用
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
E. Geist
中科院分区：
文献类型：
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作者：
E. Geist
最近开发了快速海啸模型，以根据初始地震信息(震级和震源)预测远场海啸的幅度。研究了在快速海啸模型中直接影响海啸发生的震源参数，特别注意了这些模型在当地和远场的应用。首先，可以通过测量过去事件的地震一致性来评估假设的有效性，即海啸地震的震源机制和断层类型在给定的地区是相似的。其次，假设滑动均匀地发生在破裂区域上，往往会低估当地海啸的幅度和领先波的陡度。第三，有时大震级地震会表现出高度的空间异质性，以至于海啸震源将由不同的子事件组成，这可能会在远离震源的波场中造成建设性和破坏性干扰。利用随机震源模型，证明了根据当地的水深测量，当地海啸的幅度变化可达两倍或更多。如果在滑动分布模式之外改变其他震源参数，如震源深度或剪切模数，那么对于类似震级的地震，当地海啸幅度的不确定性预计会更大。由于可用于发布当地警报的时间很短，而且本研究建议的基于模型的本地预报存在高度不确定性，直接的波高观测和强有力的公众教育和准备计划对于那些疑似海啸源头附近的地区至关重要。
Rapid tsunami models have recently been developed to forecast far-field tsunami amplitudes from initial earthquake information (magnitude and hypocenter). Earthquake source parameters that directly affect tsunami generation as used in rapid tsunami models are examined, with particular attention to local versus far-field application of those models. First, validity of the assumption that the focal mechanism and type of faulting for tsunamigenic earthquakes is similar in a given region can be evaluated by measuring the seismic consistency of past events. Second, the assumption that slip occurs uniformly over an area of rupture will most often underestimate the amplitude and leading-wave steepness of the local tsunami. Third, sometimes large magnitude earthquakes will exhibit a high degree of spatial heterogeneity such that tsunami sources will be composed of distinct sub-events that can cause constructive and destructive interference in the wavefield away from the source. Using a stochastic source model, it is demonstrated that local tsunami amplitudes vary by as much as a factor of two or more, depending on the local bathymetry. If other earthquake source parameters such as focal depth or shear modulus are varied in addition to the slip distribution patterns, even greater uncertainty in local tsunami amplitude is expected for earthquakes of similar magnitude. Because of the short amount of time available to issue local warnings and because of the high degree of uncertainty associated with local, model-based forecasts as suggested by this study, direct wave height observations and a strong public education and preparedness program are critical for those regions near suspected tsunami sources.