A four-year study of shear-wave splitting in Iceland: 2. Temporal changes before earthquakes and volcanic eruptions
A four-year study of shear-wave splitting in Iceland: 2. Temporal changes before earthquakes and volcanic eruptions
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DOI：
10.1144/gsl.sp.2003.212.01.09
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
T. Volti;S. Crampin
中科院分区：
文献类型：
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作者：
T. Volti;S. Crampin
本章报道了冰岛地震和火山爆发前分裂剪切波之间的时间延迟的时间变化。假设是，在应力积累过程中，直接震源区周围的大量裂缝分布被改变，直到裂缝水平达到断裂临界，此时剪切强度丧失，岩石破裂，地震或某些类型的火山爆发发生。在两年的时间里，当火山和岩浆活动似乎很低的时候，在3.5到5.1级地震之前，冰岛西南部的剪切波分裂的变化经常被观察到。在此较窄的振幅范围内，假定地震震级与裂缝纵横比增加速率呈线性关系，成功预测了一次M5级地震的时间和震级。这些结果证实了对原位岩石压裂前变形的新认识，这对岩石破裂时地壳在低变形水平下发生变化的广泛情况具有指导意义。这种新认识的潜在应用包括监测油气产量，以及地震和一些火山爆发的应力预测。
Abstract This chapter reports temporal variations in the time-delays between split shear-waves before both earthquakes and volcanic eruptions in Iceland. The hypothesis is that during a build-up of stress, crack distributions in a large volume surrounding the immediate source zone are modified until the level of cracking reaches fracture criticality, when shear strength is lost, rocks fracture, and earthquakes, or some types of eruptions occur. In one two-year period, when volcanic and magmatic activity appeared to be low, changes in shear-wave splitting in SW Iceland were observed routinely before earthquakes with magnitudes between M3.5 and M5.1. Assuming a linear relationship between earthquake magnitude and the rate of increasing crack aspect-ratio in this comparatively narrow amplitude range, the time and magnitude of a M5 earthquake was successfully stress-forecast. These results confirm a new understanding of pre-fracturing deformation of in situ rock that has implications over a wide range of situations where the crust undergoes changes at low levels of deformation below those at which rocks fracture. Potential applications of this new understanding include monitoring hydrocarbon production, as well as stress-forecasting earthquakes and some volcanic eruptions.