The Anisotropy and Polarization of Stress-Induced Microwave Radiation Changes in Granite and Their Significance for Seismic Remote Sensing

摘要

Incidence angles (theta) and polarization modes (p) are the essential factors for detecting earthquake (EQ)-related microwave radiation anomalies. However, their influences are still not well studied. In this article, research was carried out to simulate the observation of satellite on EQ under different theta and p. The microwave observation experiments were performed on granite samples pressed with theta from 0 degrees to 30 degrees, as well as vertical (v) to horizontal (h) polarizations under weak radiation environment. It was found that the stress-induced changes (Delta T-B) in the samples' microwave brightness temperature (TB) are anisotropic and polarized. It was observed that the trends of Delta T-B may be reversed under different theta ( p), with a probability of 57.14% (14.29%). The magnitude of Delta T-B at h is also prone to greater changes than that at v, with a probability of 67.86%. Theoretical analysis was performed based on crystal optics, Fresnel formulas, and dielectric physics. This phenomenon may relate to the combined action of piezoelectric effect, extension and contraction of ionic bonds, and turning-direction polarization. The sensitivity of T-B to the change in permittivity was analyzed by theoretical simulation in order to reveal the effects of modification in theta and p on the T-B change in stress of rock. For rocks with permittivity epsilon = 7-i0.3, the most and least sensitive theta are near 52 degrees at h polarization and 69 degrees at v polarization, respectively. Finally, the significance of these results was discussed.