Melnik Oleg, Lyakhovsky Vladimir, Shapiro Nikolai M, Galina Natalia, Bergal-Kuvikas Olga
Institute of Mechanics, Moscow State University, 1 Michurinskiy prospekt, 119192, Moscow, Russia.
Geological Survey of Israel, 32 Yesha'ayahu Leibowitz st, 9692100, Jerusalem, Israel.
Nat Commun. 2020 Aug 6;11(1):3918. doi: 10.1038/s41467-020-17759-4.
Deep long-period (DLP) earthquakes observed beneath active volcanoes are sometimes considered as precursors to eruptions. Their origin remains, however, unclear. Here, we present a possible DLP generating mechanism related to the rapid growth of gas bubbles in response to the slow decompression of over-saturated magma. For certain values of the gas and bubble content, the elastic deformation of surrounding rocks forced by the expanding bubbly magma can be fast enough to generate seismic waves. We show that amplitudes and frequencies of DLP earthquakes observed beneath the Klyuchevskoy volcano (Kamchatka, Russia) can be predicted by our model when considering pressure changes of ~10 Pa in a volume of ~10-10 m and realistic magma compositions. Our results show importance of the deep degassing in the generation of volcanic seismicity and suggest that the DLP swarms beneath active volcanoes might be related to the pulses of volatile-rich basaltic magmas rising from the mantle.
在活火山下方观测到的深部长周期（DLP）地震有时被视为火山喷发的前兆。然而，其起源仍不清楚。在此，我们提出一种可能的DLP产生机制，该机制与过饱和岩浆缓慢减压时气泡的快速生长有关。对于特定的气体和气泡含量值，由膨胀的气泡状岩浆迫使周围岩石产生的弹性变形可能足够快，从而产生地震波。我们表明，当考虑在约10⁻¹⁰立方米的体积中约10帕斯卡的压力变化以及实际的岩浆成分时，我们的模型可以预测在克柳切夫斯科伊火山（俄罗斯堪察加半岛）下方观测到的DLP地震的振幅和频率。我们的结果表明深部脱气在火山地震活动产生中的重要性，并表明活火山下方的DLP地震群可能与来自地幔的富含挥发物的玄武质岩浆脉冲有关。
