In this paper, we present numerical modeling aimed to explain Deep Long Period (DLP) events occurring in middle-to-lower crust beneath volcanoes and often observed in association with volcanic eruptions or their precursors. We consider a DLP generating mechanism caused by the rapid growth of gas bubbles in response to the slow decompression of H₂O–CO₂ over-saturated basaltic magma. The nucleation and rapid growth of gas bubbles lead to rapid pressure change in the magma and elastic rebound of the host rocks, radiating seismic waves recorded as DLP events. The magma and host rocks are modeled as Maxwell bodies with different relaxation times and elastic moduli. Simulations of a single sill-shaped intrusion with different parameters demonstrate that realistic amplitudes and frequencies of P and S seismic waves can be obtained when considering intrusions with linear sizes of the order of 100 m. We then consider a case of two closely located sills and model their interaction. We speculate on conditions that can result in consecutive triggering of the bubble growth in multiple closely located batches of magma, leading to the generation of earthquake swarms or seismic tremors.

中文翻译：

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玄武岩岩浆中气泡的快速生长是深部长周期火山地震的来源


在本文中，我们提出了数值建模，旨在解释发生在火山下方中下地壳的深长周期 （DLP） 事件，这些事件通常与火山喷发或其前兆有关。我们考虑了由气泡快速生长引起的 DLP 生成机制，以响应 H₂O-CO₂ 过饱和玄武岩岩浆的缓慢减压。气泡的成核和快速增长导致岩浆中的快速压力变化和主岩的弹性回弹，辐射出记录为 DLP 事件的地震波。岩浆岩和主岩被建模为具有不同弛豫时间和弹性模量的麦克斯韦体。对具有不同参数的单个基台形侵入体的模拟表明，当考虑线性尺寸为 100 m 的侵入体时，可以获得 P 和 S 地震波的真实振幅和频率。然后，我们考虑两个位置紧密的基台的情况，并对它们的相互作用进行建模。我们推测了可能导致在多个紧密排列的岩浆批次中连续触发气泡生长的条件，从而导致地震群或地震震颤的产生。