本文選題：地震應(yīng)力觸發(fā) + 靜態(tài)庫(kù)侖應(yīng)力變化��； 參考：《中國(guó)地震局地球物理研究所》2017年博士論文

【摘要】：地震“應(yīng)力觸發(fā)”是近年來(lái)地震科學(xué)研究中的熱點(diǎn)之一,由地震引起應(yīng)力轉(zhuǎn)移從而對(duì)后續(xù)事件產(chǎn)生觸發(fā)作用的應(yīng)力觸發(fā)模型已被大量震例的研究成果所支持。應(yīng)力觸發(fā)理論中的最關(guān)鍵問題是如何計(jì)算庫(kù)侖應(yīng)力變化,但傳統(tǒng)方法的計(jì)算一般都是基于Okada的解析解,其中不考慮流體對(duì)固體骨架力學(xué)行為的影響。同時(shí),模型中通常僅僅計(jì)算同震位錯(cuò)所產(chǎn)生的庫(kù)侖應(yīng)力變化,而不考慮震后余滑、孔隙流體遷移等其他因素造成的影響。但實(shí)際上,流體廣泛存在于地下巖土介質(zhì)中,對(duì)固體變形有著非常重要的影響。當(dāng)主震發(fā)生后,隨著時(shí)間的推移,震后余滑、介質(zhì)孔隙壓變化等震后效應(yīng)的作用逐漸突出,由此引起的靜態(tài)庫(kù)侖應(yīng)力變化也逐漸發(fā)揮作用。為此,本文基于孔隙彈性理論,考慮流-固之間的完全耦合作用,針對(duì)三種不同類型的斷層錯(cuò)動(dòng)模型(走滑型、逆沖型以及正斷型),利用有限元數(shù)值模擬方法,分別計(jì)算同震靜態(tài)庫(kù)侖應(yīng)力變化的空間分布,然后將其結(jié)果與傳統(tǒng)算法的進(jìn)行比較,考察流-固耦合的效果。在此之上,進(jìn)一步計(jì)算震后余滑、孔隙流體遷移等引起的庫(kù)侖應(yīng)力變化的時(shí)空分布,定量分析這些因素對(duì)地震觸發(fā)的影響。研究中,主要獲得的成果如下:1.三種不同類型地震模型得到的介質(zhì)孔隙壓變化在空間的分布格局完全不同:走滑型地震產(chǎn)生的同震孔隙壓變化圖案在空間中呈正負(fù)相間的四象限分布,近場(chǎng)的靜態(tài)庫(kù)侖應(yīng)力明顯下降,流-固耦合作用對(duì)靜態(tài)庫(kù)侖應(yīng)力變化的影響較大;逆沖和正斷層地震產(chǎn)生的介質(zhì)孔隙壓變化在空間的分布圖案類似,但正負(fù)區(qū)域正好相反;孔隙壓在逆沖地震的震源附近上升,而在正斷層地震的震源附近下降。同傳統(tǒng)方法計(jì)算的庫(kù)侖應(yīng)力相比,逆沖地震產(chǎn)生的介質(zhì)孔隙壓變化使得震源附近的應(yīng)力影區(qū)面積減小,這將會(huì)觸發(fā)更多的余震;而正斷層地震產(chǎn)生的孔隙壓變化則正好相反,增大了震源附近的應(yīng)力影區(qū)范圍,這樣可能會(huì)減小該區(qū)域余震發(fā)生的機(jī)會(huì)。2.三種不同類型地震的震后流體擴(kuò)散效果也很不相同:在滲透率相同的介質(zhì)中,走滑型地震的孔隙壓力變化衰減速度相對(duì)較慢,在20天內(nèi)逐漸衰減;逆沖和正斷層地震產(chǎn)生的孔隙壓變化則會(huì)在10天內(nèi)急劇降低;但三種不同類型地震的孔隙壓變化最終都會(huì)在60天后衰減完畢。雖然孔隙壓力變化會(huì)在震后不斷地演化,但由于孔隙壓力變化對(duì)庫(kù)侖應(yīng)力變化的貢獻(xiàn)所占比例較小,因而對(duì)總體靜態(tài)庫(kù)侖應(yīng)力變化的影響非常有限。由此可見,單純震后流體孔隙壓力變化對(duì)地震觸發(fā)的能力較弱,震后流體運(yùn)移觸發(fā)地震的物理機(jī)制還需深入研究。3.三種不同類型地震的震后余滑效果也很不一樣:走滑型地震的震后余滑能整體上提升庫(kù)侖應(yīng)力變化的幅度,觸發(fā)更多的地震;逆沖地震的庫(kù)侖應(yīng)力上升區(qū)域會(huì)在空間中整體擴(kuò)展,觸發(fā)范圍更大的余震;而正斷層地震的震后余滑對(duì)庫(kù)侖應(yīng)力變化的影響較小,僅沿?cái)鄬觾啥擞休^小的擴(kuò)展。4.此外,研究中還專門利用傳統(tǒng)方法計(jì)算了四川蘆山地震(MS7.0)對(duì)其余震的觸發(fā)情況。當(dāng)選擇最優(yōu)破裂面投影、或選擇余震節(jié)面投影或使用不同的震源位錯(cuò)模型以及不同的有效摩擦系數(shù)時(shí),大量的數(shù)值計(jì)算均發(fā)現(xiàn),蘆山地震對(duì)其余震沒有明顯的觸發(fā)效果�？傊�,計(jì)算地震引起的庫(kù)侖應(yīng)力變化不是一個(gè)簡(jiǎn)單的問題,它涉及地震發(fā)生、震后響應(yīng)、構(gòu)造應(yīng)力場(chǎng)和介質(zhì)環(huán)境變化等。只有充分利用數(shù)值模擬手段,考慮諸如介質(zhì)的流-固耦合等多種物理因素,才有可能獲得比較接近真實(shí)的庫(kù)侖應(yīng)力變化,從而使得地震觸發(fā)理論更為完善,更加科學(xué)合理地分析地震趨勢(shì)及評(píng)估地震災(zāi)害。
[Abstract]:Earthquake "stress triggering" is one of the hotspots in recent seismological research. The stress triggering model, which is caused by the earthquake induced stress transfer and triggering the subsequent events, has been supported by the research results of a large number of seismic examples. The key problem in the theory of stress triggering is how to calculate Coulomb stress change, but the traditional method is calculated. It is generally based on the analytic solution of Okada, which does not consider the effect of fluid on the mechanical behavior of the solid skeleton. At the same time, the model usually only calculates the Coulomb stress changes caused by the dislocation of the same earthquake, but does not consider the influence of other factors, such as the residual slip after the earthquake, the migration of pore fluid and other factors. In the mass, it has a very important influence on the deformation of the solid. After the occurrence of the main shock, the aftershock effect of the aftershock and the change of the pore pressure of the medium gradually protruded with the passage of time, and the static Coulomb stress changes caused by it gradually play a role. This paper, based on the theory of pore elasticity, takes into account the complete coupling between the flow and solid. Using three different types of fault dislocation models (strike slip type, thrust type and positive fault type), the spatial distribution of static Coulomb stress changes of the same earthquake is calculated by finite element numerical simulation method, and then the results are compared with the traditional algorithm, and the effect of the fluid solid coupling is investigated. On this, the residual slip of the earthquake is further calculated. The temporal and spatial distribution of Coulomb stress changes caused by pore fluid migration, and quantitative analysis of the effects of these factors on earthquake triggering. The main achievements in the study are as follows: 1. the distribution pattern of pore pressure changes in the medium of three different types of seismic models is completely different: the variation of pore pressure caused by a strike slip earthquake The four quadrant distribution in the space is positive and negative in the space, the static Coulomb stress of the near field decreases obviously, the flow to solid coupling has great influence on the static Coulomb stress change, and the pore pressure variation produced by the thrusting and normal fault earthquakes is similar in the spatial distribution pattern, but the positive and negative regions are just the opposite; the pore pressure is the source of the thrusting earthquake. Near the source of the normal fault earthquake, it rises near the source of the normal fault earthquake. Compared with the Coulomb stress of the traditional method, the change of pore pressure caused by the medium pore pressure caused by the thrusting earthquake reduces the area of the stress area near the source, which will trigger more aftershocks, and the pore pressure variation produced by the normal fault earthquake is just the opposite and increases near the seismic source. The scope of the stress area, this may reduce the chance of aftershock in the region.2. three different types of earthquakes after earthquake fluid diffusion effect is very different: in the medium with the same permeability, the attenuation velocity of the pore pressure change of the strike slip earthquake is relatively slow, gradually attenuates in 20 days, and the pore of the thrusting and normal fault earthquakes The pressure change will decrease sharply in 10 days, but the pore pressure changes in the three different types of earthquakes will eventually decay after 60 days. Although the pore pressure changes will continue to evolve after the earthquake, the contribution of the pore pressure changes to the Coulomb stress change is smaller, so the influence on the overall static Coulomb stress change is not. It can be seen from this, it can be seen that the fluid pore pressure change after the simple earthquake is weak to the earthquake triggering, and the physical mechanism of the fluid migration triggering the earthquake after the earthquake is also necessary to study the residual slip effect of the.3. three different types of earthquakes after the earthquake. More earthquakes, the Coulomb stress rising region of the thrusting earthquake will expand in the whole space and trigger a larger aftershock, while the residual slip of the positive fault earthquake has little influence on the Coulomb stress change, and only along the faults at both ends of the fault has a small expansion.4.. In the study, the Sichuan Lushan earthquake (MS7.0) is also calculated by the traditional method. A large number of numerical calculations show that the Lushan earthquake has no obvious triggering effect on its aftershocks when selecting the optimal projection surface, or selecting the aftershock surface projection or using different seismic source dislocation models and different effective friction coefficients. In a word, the Coulomb stress changes caused by the calculation of the earthquake are not one. A simple problem involves the occurrence of earthquakes, the response of the earthquake, the tectonic stress field and the change of the medium environment. Only by making full use of the numerical simulation methods and considering various physical factors such as the fluid solid coupling of the medium, it is possible to get more close to the real Coulomb stress change, which makes the theory of earthquake triggering more perfect and more scientific. Learn to analyze earthquake trend reasonably and evaluate earthquake disaster.

【學(xué)位授予單位】：中國(guó)地震局地球物理研究所
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：P315

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