与地震预测预报有关的几个物理问题

文章简要介绍了与地震预测预报有关的几个物理问题,包括地震活动性问题、地球深部物质的物理性质及其变化问题、地球深部的流体问题、地震破裂问题、地球深部的形变和应力问题.这些问题的研究涉及当代物理学的一前沿领域.唐山大地震后30年来有诸多重要进展.     

寂静地震与地震预测的物理问题

寂静地震是指发生了缓慢的位错、但几乎不辐射地震波的“地震” .在目前的地震预测的物理学研究中 ,通常是通过计算历史上曾经发生过的地震所引起的应力变化 ,或者通过研究地震活动的统计性质或“图像动力学” ,来推测一个断层带上发生地震的危险性 .寂静地震的信息的缺失 ,形成了地震预测的物理学研究中的一个很大的“盲区” ,而在相当程度上 ,解决地震预测的物理问题的主要困难和可能的突破的希望 ,也许就在于此 .寂静地震的研究目前还很不深入 .关于寂静地震的性质 ,文章作者提出两个猜想 :(1)寂静地震的频度 ,满足类似于GR定律的幂律分布 ;(2 )最大的寂静地震的地震矩 ,与“可见”的最大地震的地震矩相当 .     

地震预测与统计物理

将现代统计物理学的理论和方法应用于地震和地震预测问题的研究，近年来取得了长足的进展，成为物理学和地震学之间一个最为活跃的交叉领域，这一领域所取得的成果，例如，将地震作为一种临界现象的模型，不仅丰富和深化了对地震的认识，而且改变了地震预测研究中的一些传统观念。文章介绍了这方面的研究进展，讨论了与这一领域相关的一些重要的物理概念和悬而未决的科学问题。     

减轻地震灾害的物理学问题

减轻地震灾害的研究通常包括地震危险性评估、地震危害预测、地震灾害的减轻三个环节．物理学在减轻地震灾害的研究与应用中具有重要意义．文章从强地面运动与地震的工程灾害、复杂系统与地震的社会灾害、地球应力场的变化与地震预测等三个不同的侧面，介绍了在减轻地震灾害的实际工作中提出的一些重要的物理问题．这些问题既是目前地震学家、工程地震学家和地震工程师普遍关注的基础科学问题，也同时与当代物理学研究的一些前沿领域紧密地联系在一起．     

以颗粒物理原理认识地震——地震成因、地震前兆和地震预测

本文以地壳和地幔的基本构造和己有观测事实为依据,运用颗粒物理原理,将地壳和地幔作为大尺度离散态颗粒物质体系处理,重新认识地震孕育过程,前兆产生机制及规律,探求地震预测方法和途径.主要结果是:建立了地壳与地幔构成和运动的颗粒模型;提出了引发地震的大地构造力的形成机制,以及地震前兆信息产生和传播规律;说明了地震前兆信息的主要特征及其与地震发生之间的关联,阐述了探测有效地震前兆信息的方法原理;用颗粒流动的阻塞-解阻塞转变原理解释了深源地震发生机制;对以前难以理解的若干地震学现象进行了解释,并讨论了地震的可预测性。由于地壳和地幔的离散结构特征,对于地震孕育的准静力学过程,连续介质理论不再适用.以颗粒物理原理研究地震成因、地震前兆和地震预测,所获得的新认识与传统连续介质地震学观点有本质区别。     

地震数值预报*

地震能否预报、地震预报遇到的种种困难如何克服?在思考这一问题时,不妨借助于气象预报的经验.气象预报从经验预报发展到数值预报,虽然用了约半个世纪的时间,但获得了成功.中国地震学界,对于地震预报的发展,也必须从经验预报发展为物理预报,对此几乎没有异议;但是物理预报的基本特点就是要基于定量的物理规律,进行数值预报,却鲜被提及.文章讨论了开展地震数值预报的五个主要环节的现状,认为地震数值预报现在应该提到规划的日程上来,设计我国地震数值预报的路线图,按照它的需要部署地震台站观测工作,开展地震数值预报的理论探讨.     

从非线性与统计物理多重角度探讨数值地震预测

在科技文献中,地震常被比喻为非线性动力学过程或统计物理中的相变过程.文章探讨了如何从非线性力学中的分岔理论以及统计物理内的朗道相变理论出发,从势磊穿越,临界涨落与临界慢化等多个角度来分析和了解地震发生的全过程.文章作者试图在这些非线性力学与统计物理的基础上,综合地震过程中在时间与空间上应出现的前兆,解释如何可能做出具有普适性的数值地震预测.     

海啸、地震海啸与海啸地震

简要地介绍了海啸与地震海啸的成因、特点,分析了影响地震海啸的重要因素,阐述了海啸预警的物理基础.以2004年12月26日苏门答腊-安达曼MW9.0特大地震及其激发的印度洋特大海啸为例,说明除了地震的大小、地震机制、震源深度以外,震源破裂过程也是影响地震激发海啸的重要因素.通过对苏门答腊-安达曼特大地震及2005年3月28日苏门答腊北部特大地震进行分析对比,探讨了海啸地震的特征,阐明了进一步深入研究海啸地震的特征及其激发海啸的机制对于预防和减轻海啸灾害的重要意义.     

从弹簧滑块到地震预测:BK模型今昔谈

Burridge-Knopoff弹簧－滑块模型作为一个概念性的地震模型，自1967年提出以来一直为地震学家和物理学家所关注，对BK模型的研究成为物理学与地震学之间的一个活跃的交叉领域，BK模型的一些性质，例如确定性浑沌，自组织，孤立波，等等，能够为理解地震的性质和解决地震预测问题提供有用的线索，BK模型与目前的一些悬而未决的复杂性物理问题的联系，使它不仅对地震研究，而且对更普遍的多体系统问题的研究，都有重要的影响。     

对图像信息学(PI)算法的一个回溯性预测检验:四川芦山7.0级地震

文章针对中强地震预测的图像信息学(PI)算法,对2013年4月20日芦山Ms7.0地震的预测效果进行了回溯性震例分析.结果表明,在芦山地震的震中附近存在“PI热点”.在与2008年汶川地震的PI算法预测进行比较后建议,在以后的“PI热点”计算中,也许还应把背景形变速率作为一个权重因素考虑在内.     

海啸的物理

地震海啸的产生是地球表面固体层和流体层相互作用的结果．文章介绍了这种相互作用的物理过程，讨论了海啸的大小、能量、传播速度．指出：建立早期预警系统是减少海啸灾害的重要措施，目前的预警系统虚报率很高的问题，仍需要通过加强地球表层系统相互作用的研究来解决．     

The Effect of Catalogue Lead Time on Medium-Term Earthquake Forecasting with Application to New Zealand Data

‘Every Earthquake a Precursor According to Scale’ (EEPAS) is a catalogue-based model to forecast earthquakes within the coming months, years and decades, depending on magnitude. EEPAS has been shown to perform well in seismically active regions like New Zealand (NZ). It is based on the observation that seismicity increases prior to major earthquakes. This increase follows predictive scaling relations. For larger target earthquakes, the precursor time is longer and precursory seismicity may have occurred prior to the start of the catalogue. Here, we derive a formula for the completeness of precursory earthquake contributions to a target earthquake as a function of its magnitude and lead time, where the lead time is the length of time from the start of the catalogue to its time of occurrence. We develop two new versions of EEPAS and apply them to NZ data. The Fixed Lead time EEPAS (FLEEPAS) model is used to examine the effect of the lead time on forecasting, and the Fixed Lead time Compensated EEPAS (FLCEEPAS) model compensates for incompleteness of precursory earthquake contributions. FLEEPAS reveals a space-time trade-off of precursory seismicity that requires further investigation. Both models improve forecasting performance at short lead times, although the improvement is achieved in different ways.     

The diversity of the physics of earthquakes

Earthquakes exhibit diverse characteristics. Most shallow earthquakes are “brittle” in the sense that they excite seismic waves efficiently. However, some earthquakes are slow, as characterized by tsunami earthquakes and even slower events without any obvious seismic radiation. Also, some earthquakes, like the 1994 Bolivian deep earthquake, involved a large amount of fracture and thermal energy and may be more appropriately called a thermal event, rather than an earthquake. Some earthquakes are caused by processes other than faulting, such as landslides. This diversity can be best understood in terms of the difference in the partition of the released potential energy to radiated, fracture, and thermal energies during an earthquake. This approach requires detailed studies on quantification of earthquakes and estimation of various kinds of energies involved in earthquake processes. This paper reviews the progress in this field from historical and personal points of view and discusses its implications for earthquake damage mitigation.     

Self-Organized Criticality in an Anisotropic Earthquake Model

We have made an extensive numerical study of a modified model proposed by Olami,Feder,and Christensen to describe earthquake behavior.Two situations were considered in this paper.One situation is that the energy of the unstable site is redistributed to its nearest neighbors randomly not averagely and keeps itself to zero.The other situation is that the energy of the unstable site is redistributed to its nearest neighbors randomly and keeps some energy for itself instead of reset to zero.Different boundary conditions were considered as well.By analyzing the distribution of earthquake sizes,we found that self-organized criticality can be excited only in the conservative case or the approximate conservative case in the above situations.Some evidence indicated that the critical exponent of both above situations and the original OFC model tend to the same result in the conservative case.The only difference is that the avalanche size in the original model is bigger.This result may be closer to the real world,after all,every crust plate size is different.     

Modeling fast and slow earthquakes at various scales

Earthquake sources represent dynamic rupture within rocky materials at depth and often can be modeled as propagating shear slip controlled by friction laws. These laws provide boundary conditions on fault planes embedded in elastic media. Recent developments in observation networks, laboratory experiments, and methods of data analysis have expanded our knowledge of the physics of earthquakes. Newly discovered slow earthquakes are qualitatively different phenomena from ordinary fast earthquakes and provide independent information on slow deformation at depth. Many numerical simulations have been carried out to model both fast and slow earthquakes, but problems remain, especially with scaling laws. Some mechanisms are required to explain the power-law nature of earthquake rupture and the lack of characteristic length. Conceptual models that include a hierarchical structure over a wide range of scales would be helpful for characterizing diverse behavior in different seismic regions and for improving probabilistic forecasts of earthquakes.