Xiang-Chu Yin

A new approach to earthquake prediction: The Load/Unload Response Ratio (LURR) theory

The response to loading is different from that to unloading when the focal media is approaching instability. The ratio of the response rate during loading to that during unloading, called Load/Unload Response RatioY (LURR), could be a measure of the closeness degree to instability and is used in a new approach to earthquake prediction. Retrospective examination of some one hundred earthquake cases (fromM 4 toM 8.6) indicates that for more than 80% of the examined ones, the value ofY is much higher than 1 for a period before the main shock, but theY value always fluctuates slightly about 1 during two decades for seven stable regions, so that the parameterY value always fluctuates slightly degree of an impending earthquake. Several earthquakes occurring on the Chinese mainland in recent years as well as the Northridge California, U.S.A. earthquake (Jan. 17, 1994,Mw 6.7) have been predicted beforehand with this method.

Development of a New Approach to Earthquake Prediction: Load:Unload Response Ratio (LURR) Theory

Abstract—The seismogenic process is nonlinear and irreversible so that the response to loading is different from unloading. This difference reflects the damage of a loaded material. Based on this insight, a new parameter-load/unload response ratio (LURR) was proposed to measure quantitatively the proximity to rock failure and earthquake more than ten years ago. In the present paper, we review the fundamental concept of LURR, the validation of LURR with experimental and numerical simulation, the retrospective examination of LURR with new cases in different tectonic settings (California, USA, and Kanto region, Japan), the statistics of earthquake prediction in terms of LURR theory and the random distribution of LURR under Poissons model. Finally we discuss LURR as a parameter to judge the closeness degree to SOC state of the system and the measurement of tidal triggering earthquake.¶The Load/Unload Response Ratio (LURR) theory was first proposed in 1984 (Yin, 1987). Subsequently, a series of advances were made (Yin and dYin, 1991; Yin, 1993; Yin et al. 1994a, b, 1995; Maruyama, 1995). In this paper, the new results after 1995 are summarized (Yin et al., 1996; Wang et al., 1998a; Zhuang and Yin, 1999).

Numerical Simulation of Rock Failure and Earthquake Process on Mesoscopic Scale

Abstract—On the basis of the lattice model of Mora and Place, Discrete Element Method, and Molecular Dynamics approach, another kind of numerical model is developed. The model consists of a 2-D set of particles linked by three kinds of interactions and arranged into triangular lattice. After the fracture criterion and rules of changes between linking states are given, the particle positions, velocities and accelerations at every time step are calculated using a finite-difference scheme, and the configuration of particles can be gained step by step. Using this model, realistic fracture simulations of brittle solid (especially under pressure) and simulation of earthquake dynamics are made.

Evolution-induced Catastrophe and its Predictability

Both earthquake prediction and failure prediction of disordered brittle media are difficult and complicated problems and they might have something in common. In order to search for clues for earthquake prediction, the common features of failure in a simple nonlinear dynamical model resembling disordered brittle media are examined. It is found that the failure manifests evolution-induced catastrophe (EIC), i.e., the abrupt transition from globally stable (GS) accumulation of damage to catastrophic failure. A distinct feature is the significant uncertainty of catastrophe, called sample-specificity. Consequently, it is impossible to make a deterministic prediction macroscopically. This is similar to the question of predictability of earthquakes. However, our model shows that strong stress fluctuations may be an immediate precursor of catastrophic failure statistically. This might provide clues for earthquake forecasting.

Damage Localization as a Possible Precursor of Earthquake Rupture

Based on the concepts of statistical mesoscopic damage mechanics, the rupture of a heterogeneous medium is investigated in terms of numerical simulations of a network model, subjected to simple shear loading. The heterogeneities are simulated by varying the sizes and fracture strains of the elements of the network. Progressive damage is governed by a damage field equation and a dynamic function of damage (DFD). From the damage field equation, a criterion for damage localization can be derived, and the DFD can be extracted from the simulations of the network. Importantly, the DFD intrinsically governs the damage localization. Both stress-free and periodic boundary conditions for the network are examined. It is found that damage localization may be the underlying mechanism of eventual rupture and thus could be used as a possible precursor of earthquake rupture.

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.

Study on the Earthquake Potential Regions in North and Northeast China by Pattern Informatics Method

The Pattern Informatics (PI) method is a new approach to forecast earthquake based on statistical physics. In general, the PI method works for long-term earthquake forecast, but we can obtain the higher spatial resolution of abnormal regions by it. In this paper, we applied the PI method to study seismic risk assessment in north and northeast China. The research suggests that there might be earthquakes with M ges 7 in the juncture of Shanxi, Henan and Shanxi provinces, the juncture of Hebei, Shandong and Henan provinces, and southeast coast of Jiangsu province from Jan. 2009 to Jan. 2050.

The China ACES-iSERVO grid node

China is establishing an advanced supercomputing environment, called the ACES-iSERVO grid node, aimed at furthering the study of earthquake prediction and modeling. This article describes the history of the China ACES-iSERVO grid node, the necessities for establishing it, its current status, and its future development.

Computation Earthquake Physics PART II: Introduction

Large earthquakes are catastrophic natural disasters which can potentially cause massive casulaties and huge property loss. In the beginning of the new century, large earthquakes violently struck the world, especially in the Asia-Pacific region. Nearly 300,000 people were killed by the magnitude 9.0 Northern Sumatra Earthquake and tsunami, and the magnitude 7.8 Pakistan earthquake of October 8th, 2005, which resulted in 90,000 deaths. In the meantime, there has been great progress in computational earthquake physics. New understanding of earthquake processes, numerous ideas on earthquake dynamics and complexity, next-generation numerical models and methods, higher performance supercomputers, and new data and analysis methods are emerging. These include the SERVO gird and iSERVO, LSM (Lattice Solid particle simulation Model); Australian Computational Earth Systems Simulator (ACcESS); Japan’s Earth Simulator; GeoFEM; GeoFEST; QuakeSim; LURR (Load-Unload Response Ratio); earthquake Critical Point Hypothesis, PI (Pattern Informatics), Critical Sensitivity, friction laws and seismicity, episodic tremor, the Virtual California model, interaction between faults and the interactions between earthquakes, ROC (Receiver Operating Characteristic), SMDM (Statistical Mesoscopic Damage Mechanics) and MFEM (Multi-scale Finite-Element Model), among others.