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与最近地震及火山事件可能有关的磁、电和电磁场变化的新观测,已经在日本云仙火山、印度洋留尼汪岛、加州朗瓦利火山、中国与俄罗斯的断层、加州圣安德烈斯断层和其他几个地区中获得。对于火山事件,可以确定在各个喷发阶段中,由不同物理过程所引起的贡献。缓慢过程(几周到几月)包括近地表的热退磁效应、压磁效应以及由磁化物质旋转/移动所引起的效应。快速过程(数秒至数天)包括由伴随爆炸型喷发的瞬间应力重新分布导致的压磁效应和由火山区常有的高液压部分的破裂所导致的电动效应。对于地震事件,在确保磁力仪探头对地震晃动不敏感且处于磁场梯度低的地方的情况下,所观测的同震偏移是瞬时的。基于大地测量与地震所确定的断层参数,压磁位错的简化模式在数量与符号方面均与所观测到的信号相一致。在流体静压力至岩石静压力的条件下,流体充满部分的破裂所产生的电动效应可产生100～0.01Hz频段的瞬时信号。然而,大地震之前数秒至数周内,震中区的近场测量并未见明显的大尺度流体的驱动过程。由地震和火山喷发引起的捕获大气层压力波(又称重力波和/或声学波、运行性电离层扰动或TID扰动)所导致的电离层扰动是共有的,并且传播到很远。这些是地震与火山爆发所期望的结果,它必须从与地震活动相关的电离层扰动之前的VLF/ULF电磁场记录中加以鉴别,并从中消除其效应。
New observations of changes in magnetism, electricity and electromagnetic fields that may have been associated with recent earthquakes and volcanic events have been reported in Japan’s Unzen volcano, the Reunion island in the Indian Ocean, the Long Valley volcano in California, the fault between China and Russia, San Andres, California Faults and several other areas are obtained. For volcanic events, the contribution of different physical processes in each eruption phase can be determined. The slow processes (weeks to months) include thermal demagnetization effects near the surface, the effect of the piezomagnetic effect and the effects caused by the rotation / movement of the magnetized material. The fast processes (seconds to days) include the effect of the piezomagnetic effect due to the instantaneous stress redistribution accompanying the explosive eruption and the electromotive effect caused by the rupture of the often high hydraulic part of the volcano. For seismic events, the observed coseismic migration is instantaneous in ensuring that the magnetometer probe is insensitive to seismic shaking and in places with low magnetic field gradients. Based on the fault parameters determined by geodesy and earthquakes, the simplified model of the pressure-magnetic dislocation coincides with the observed signal both quantitatively and symbolically. Under the condition of hydrostatic pressure to rock static pressure, the electrodynamic effect caused by the rupture of the fluid filled part can generate an instantaneous signal in the frequency band of 100~0.01 Hz. However, near-field measurements of the epicentral region did not reveal significant large-scale fluid drive in seconds or weeks prior to the earthquake. The ionospheric disturbances caused by the capture of atmospheric pressure waves (aka gravity waves and / or acoustic waves, operational ionospheric disturbances or TID disturbances) caused by earthquakes and volcanic eruptions are common and spread far. These are the result of earthquakes and volcanic eruptions that must be identified and eliminated from the VLF / ULF electromagnetic field records prior to the ionospheric perturbations associated with the seismic activity.