加卸载响应比(LURR)理论的实验研究

利用大尺度岩石试件破坏声发射实验，对加卸载响应比(Load/Unload Response Ratio)理论进行了实验研究。实验采用的加载条件力求能够模拟地下岩石的复杂受力过程。在加载过程中，岩石试件内部出现的损伤用声发射技术进行了记录。实验数据经过分析之后所得的结论与加卸载响应比理论预测的结果相符合。把加卸载响应比值Y的变化情况与声发射事件定位的过程相对比，也可以进一步看出岩石材料内部的损伤发展过程与加卸载响应比Y值的变化具有一致性。而高Y值的异常情况出现，又是在材料发生最终破坏之前，所以，可以用加卸载响应比理论定量地分析岩石试件损伤演化情况，从而对岩石材料的破坏及地震做出预测。实验结果再一次验证了加卸载响应比理论。     

加卸载响应比理论用于矿震预测的初步研究

加卸载响应比(LURR)理论是一种前景很好的中期地震预测方法,通常在强烈地震发生前的数月至1～2年LURR出现高值,因而LURR可以作为强烈天然地震的前兆,用此方法曾经成功地预测过Northridge地震(1994年1月17日,M6.7,美国加州),Kanto地震(1996年9月11日,M6.6,日本)及不少发生在中国的天然地震。用房山煤矿1992年8月至1993年7月的微震资料,计算了全年内7组M>2.1矿震前的加卸载响应比Y值,其中5组矿震前Y值均明显大于1(Y≥2.9)。以上结果表明,加卸载响应比理论有可能用于矿震的预测。     

关于加卸载响应比理论运用于地震预测的几点思考

加卸载响应比理论已在地震预测中得到广泛应用，但也面临挑战。本对加卸载响应比理论及方法进行了分析，并提出该理论几个可能的研究方面：(1)根据固体潮应力变化值给定每个小地震Benio盯应变在加卸载响应比计算中的权重；(2)考虑地震之前应力空间分布，确定加卸载响应比可能升高的区域形状，进而确定加卸载响应比计算中小震资料的选取范围；(3)将实测的小震震源机制与假定小震震源机制都相同时的加卸载响应比计算结果进行比较，研究测定的小震震源机制对加卸载响应比方法的改善情况；(4)研究加卸载响应比方法对不同震源机制类型地震的适用情况。     

赣粤闽交界及邻区近年中强地震加卸载响应比特征研究

以地震应变能作为响应因子,研究了1997至2007年赣粤闽交界及邻区4．0级（ML≥4．0）以上中强地震临震前的加卸载响应比（Y值）的基本变化特征,研究结果表明,80％以上的地震在临震前Y值呈现出高值异常形态。因而它可以作为此地区地震预测的一种手段。     

地下水位固体潮响应的地震异常

本文从理论上讨论了承压井水位与含水层固体潮体应变的关系以及在非线性失稳状态井水位对固体潮响应的变化,重点讨论了其响应率与响应比的变化。对水位观测资料的计算分析表明,震前响应率有一些变化,响应比有一个背景值1,与理论是一致的,而且震前也存在一些变化,说明水位固体潮响应可以反映含水层岩石参数的变化。     

加卸载响应比在体应变固体潮中的应用

从岩石的应变与应力的非线性响应分析了体应变固体潮加卸载响应比的物理机理, 给出了体应变固体潮加卸载响应比的计算方法,并以昌平和峰峰台的体应变观测值为例,计算了二台的体应变固体潮加卸载响应比。结果表明,在中强地震前存在增大变化。     

新疆04井水位固体潮加卸载响应比的研究

根据加卸载响应比理论,利用１９９０～１９９７年新疆０４井水位动态观测资料,分析了井水位对地球固体潮汐的响应。通过彼尔采夫滤波、气压和水位相关分析,剔除水位长趋势变化和气压的影响,计算出井水位固体潮体应变的响应率,合理地选取加载和卸载的时段,得出水位固体潮加卸载响应比,其值为１左右。水位固体潮加卸载响应比变化特征为年变平稳、幅度小,在中强地震活动时出现比值短期增高现象,异常大多出现在震前１～３个月内     

黑龙江及周边地区中强地震前加卸载响应比特征分析

选取所研究区域地震能量的贝尼奥夫应变(相当于室内岩石实验中的声发射)作为响应,以黑龙江及其周边地区2005年以来14次ML 5.0以上地震作为震例,检验卸载响应比理论的预测效果,提取异常特征,初步总结该方法的时、空、强预测指标,发现具有一定的预报效能。     

地表潮汐应变观测的响应比及特征

运用非线性系统加卸载响应比理论，研究了潮汐应变观测的响应比特征，解决了响应比理论应用中的两个基础问题：加、卸载荷的计算和潮汐前兆观测中加卸载响应比的计算模型选择潮汐应变观测中的一些潮汐和非潮汐的以及与孕震力学过程有关的信息为响应参量，在不同的加、卸载方式下对各种响应比的震兆变化及特征进行研究，研究结果表明，加卸载响应比只在非线性系统的输入与系统的失稳密切相关时，才显示出失稳的前兆特征，且主要表现为短临前兆。     

加卸载响应比与其它地震前兆时空演化研究及其应用

本文重点研究了加卸载响应比的时空演化特征 ,并利用震例研究了长期地震活动性的时空演变特征的普适性。为了理解以上特征及地震前兆综合特征 ,应用解析、数值模拟等方法对二维圆形包体、二维硬软复合包体进行了研究 ,并推导出半无限流变介质中三维包体产生的粘弹性位移、应变、地倾斜解析表达式 ,详细地计算和分析了球形包体在地表产生的体应变的时空演变过程 ,从而使孕震模型理论化。应用理论研究结果 ,对地震前兆的时空演化进行了解释 ,提出了长期预测和中短期预测方法 ,并应用于实践 ,取得 5次地震的长期、中期预测的成效。主要结果如下…     

Load-Unload Response Ratio and Accelerating Moment/Energy Release Critical Region Scaling and Earthquake Prediction

-- The main idea of the Load-Unload Response Ratio (LURR) is that when a system is stable, its response to loading corresponds to its response to unloading, whereas when the system is approaching an unstable state, the response to loading and unloading becomes quite different. High LURR values and observations of Accelerating Moment/Energy Release (AMR/AER) prior to large earthquakes have led different research groups to suggest intermediate-term earthquake prediction is possible and imply that the LURR and AMR/AER observations may have a similar physical origin. To study this possibility, we conducted a retrospective examination of several Australian and Chinese earthquakes with magnitudes ranging from 5.0 to 7.9, including Australia's deadly Newcastle earthquake and the devastating Tangshan earthquake. Both LURR values and best-fit power-law time-to-failure functions were computed using data within a range of distances from the epicenter. Like the best-fit power-law fits in AMR/AER, the LURR value was optimal using data within a certain epicentral distance implying a critical region for LURR. Furthermore, LURR critical region size scales with mainshock magnitude and is similar to the AMR/AER critical region size. These results suggest a common physical origin for both the AMR/AER and LURR observations. Further research may provide clues that yield an understanding of this mechanism and help lead to a solid foundation for intermediate-term earthquake prediction.     

新疆中强地震前加卸载响应比时空演化特征分析与检验

加卸载响应比是一种刻画震源区介质损伤程度的物理学参数,它通过随时间的变化来反映地震孕育的过程来进行地震预测。通过对1990—1999年新疆地区部分中强地震前加卸载响应比时空演化特征进行分析,并基于该理论得到孕震积分的概念应用于震例中。结果表明:中强震震前在震中附近可能存在多个高加卸载响应比值区,它们大致围成椭圆状或环状,地震通常发生在异常高值波动或减弱的过程中;异常峰值至发震时间比理论时间要短,这可能表明新疆地区构造活动剧烈,孕震周期较短。     

郯庐断裂带南段加卸载响应比变化特征分析

本文对郯庐断裂带南段开展了分段加卸载响应比变化研究,总结了区域内显著地震前加卸载响应比时序曲线的变化特征。研究表明,加卸载响应比表征了地下介质的损伤程度,具有明确的物理意义,在实际应用中取得了较好的效果。在中小地震较为丰富的研究区域,加卸载响应比在显著地震前会出现短临高值异常; 而在中小地震活动水平不高的区域,加卸载响应比在震前更多地表现为长期的背景高值异常。     

Simulation of the Load-Unload Response Ratio and Critical Sensitivity in the Lattice Solid Model

— The Load-Unload Response Ratio (LURR) method is an intermediate-term earthquake prediction approach that has shown considerable promise. It involves calculating the ratio of a specified energy release measure during loading and unloading where loading and unloading periods are determined from the earth tide induced perturbations in the Coulomb Failure Stress on optimally oriented faults. In the lead-up to large earthquakes, high LURR values are frequently observed a few months or years prior to the event. These signals may have a similar origin to the observed accelerating seismic moment release (AMR) prior to many large earthquakes or may be due to critical sensitivity of the crust when a large earthquake is imminent. As a first step towards studying the underlying physical mechanism for the LURR observations, numerical studies are conducted using the particle based lattice solid model (LSM) to determine whether LURR observations can be reproduced. The model is initialized as a heterogeneous 2-D block made up of random-sized particles bonded by elastic-brittle links. The system is subjected to uniaxial compression from rigid driving plates on the upper and lower edges of the model. Experiments are conducted using both strain and stress control to load the plates. A sinusoidal stress perturbation is added to the gradual compressional loading to simulate loading and unloading cycles and LURR is calculated. The results reproduce signals similar to those observed in earthquake prediction practice with a high LURR value followed by a sudden drop prior to macroscopic failure of the sample. The results suggest that LURR provides a good predictor for catastrophic failure in elastic-brittle systems and motivate further research to study the underlying physical mechanisms and statistical properties of high LURR values. The results provide encouragement for earthquake prediction research and the use of advanced simulation models to probe the physics of earthquakes.     

青海玛多MS7.4地震前LURR与OLR短临异常关联性研究

加卸载响应比(LURR)是根据岩石应力-应变关系的动态演化规律提出的地震预测方法。以Benioff应变为响应量,分析青海玛多M_S7.4地震前震中及其周边400 km内的LURR异常的演化特征发现,在震前一个月LURR值达到最高值,半个月之后出现高值回落的现象,说明此时孕震区岩石介质已进入屈服阶段的末端。在此基础上,利用NOAA卫星地面长波辐射(OLR)数据,分析高值回落后(5月14—25日)地面长波辐射值的短临异常演化规律。结果显示:震前在空间上仅仅在震中北部出现OLR显著且连续的短临异常变化并呈现向震中扩展的趋势,在时间上整个演化过程经历了初始增温-异常扩展-达到峰值-异常减弱-地震发生-异常消失等6个阶段。LURR和OLR震前短临异常特征说明,回落前的LURR高值反映了岩石介质屈服阶段的结束,OLR在一定程度上可以表征处于临界状态的活动断层的构造应力累积状态,综合研究两种物理参量震前异常演化特征,有助于更准确评估地震活动趋势。     

地震预测的加卸载响应比岩石实验模拟

我们在中科院力学所非线性连续介质力放实验室材料试验机上做了岩石压缩破坏的加卸载实验,得到了以应变为尖的加卸载响应比。     

加卸载响应比的数值模拟

用数值模型来模拟和验证加卸载响应比（ＬＵＲＲＬｏａｄ／Ｕｎｌｏａｄ　ＲｅｓｐｏｎｓｅＲａｔｉｏ）理论．编制非均匀各向异性材料宏细观损伤破坏程序,模拟固体材料在损伤破坏时的加卸载过程,证实了加卸载响应比理论的正确性．结果表明,ＬＵＲＲ这一反映地球介质临近破坏的指标,也可以用来预测材料的破坏．同时讨论了一些参数（如均匀程度和脆性程序）对ＬＵＲＲ的影响,发现材料越呈脆性,或越均匀,ＬＵＲＲ值上升得越晚,曲线越陡．该结果对用ＬＵＲＲ指标预测地震具有一定启发．     

Failure Potential Evaluation in Engineering Experiments Using Load/Unload Response Ratio Method

The Load/Unload Response Ratio (LURR) method is proposed for prediction of the failure of brittle heterogeneous materials. Application of the method typically involves evaluating the external load on materials or structures, differentiating between loading and unloading periods, determining the failure response during both periods from data input, and calculating the ratio between the two response rates. According to the method, the LURR time series usually climbs to an anomalously high peak prior to the macro-fracture. To show the validity of the approach in engineering practice, we applied it to the loading and unloading experimental data associated with a two-floor concrete-brick structure. Results show that the LURR time series of the two floors consists of the damage evolution of the structure: they are at low level for most of the time, and reach the maxima prior to the final fracture. We then attempt to combine the LURR values with damage variable (D) to provide the health assessment of the structure. The relationship between LURR and D, defined as a function of Weibull stochastic distribution, is set up to provide more detailed underlying physical means to study damage evolution of the structure. The fact that the damage evolution of the structure correlates well with the variation of LURR time series may suggest that the LURR approach can be severed as a useful tool to provide the health assessment to big scale structures or ancient buildings.     

The Experimental Simulation of Rocks on Load/Unload Response Ratio for Earthquake Prediction

The load/unload experiments on rock failure under pressure have been carried out in Material Test System (MTS) in the Laboratory for Non-linear Mechanics of Continuous Media (LNM), Institute of Mechanics, Chinese Academy of Sciences, and load/unload response ratio (LURR) values with strain as response (i.e. inverse elastic constant as response rate) have been obtained. The experimental results are in accordance with theoretical results and those in real earthquakes: LURR rises just before rock failure. So LURR can be used as the precursor of rock failure and earthquake prediction.