Abstract

Seismicity began to be recorded in October 2017 around the dormant Bolshaya Udina Volcano (B. Udina in what follows) situated 10 km southeast of Plosky Tolbachik Volcano. Seismic tomography showed the existence of a long-lived magma chamber south of B. Udina in the area of the Tolud River. The chamber has its top at a depth of about 15 km, and may probably be connected to the Plosky Tolbachik plumbing system (Koulakov et al., 2017). Saltykov et al. (2018) and Koulakov et al. (2019) related the observed resumption of seismic activity to a hypothetical emplacement of magma beneath the Udina volcanoes, pointing out a high likelihood of the resumption of volcanic activity. The present study examines data from permanent seismic stations showing a systematic displacement of the center of seismic energy southward from B. Udina from October 2017 through August 2019. The center characterizes the location of the volume that generates the bulk of seismicity. We used images of the Sentinel-1A satellite (wavelength 5.6 cm) taken from a descending orbit of track 60 during the period from June 7, 2017 through September 23, 2017 (10 images) and during the period from May 21, 2018 to September 30, 2018 (12 images) to determine time series and average velocities of displacement on the slopes of B. Udina. Persistent scatterers could only be identified at the foot of B. Udina. An analysis of displacement time series for the surface of the volcano showed that the character of displacements in 2017 and 2018 on the southwestern and eastern slopes remained nearly the same, while the average rate of displacement on the northwestern slope decreased in 2018. We used three images of the ALOS-2 PALSAR-2 satellite (wavelength 23.5 cm) taken on October 4, 2016, June 13, 2016, and October 2, 2018 from an ascending orbit to construct paired interferograms, which characterize displacements for the time period between images. The displacements on both interferograms did not exceed a few centimeters, except for narrow zones confined to local relief forms. The deformations thus detected were most likely due to surface processes. The deformed volumes related to pressure changes in the magma chamber at a depth of 5 km must have linear dimensions of 10–15 km, while the displacement areas detected in the satellite images are considerably smaller. These results suggested an alternative model that postulates the resumption of seismic activity to accompany the retreat and sinking of magma melt from B. Udina into the chamber in the Tolud R. area as identified by tomographic techniques.

中文翻译：

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地震和SAR干涉测量学联合研究以评估Dormant Bolshaya Udina火山爆发的可能性

摘要

自2017年10月开始，位于Plosky Tolbachik火山东南10公里处的休眠Bolshaya Udina火山（以下简称B.Udina）周围发生地震。地震层析成像显示，在托鲁德河地区，乌迪纳以南存在着一个长寿命的岩浆室。该室的顶部深度约15 km，可能与Plosky Tolbachik管道系统相连（Koulakov等人，2017）。Saltykov等。（2018）和Koulakov等人。（2019）将观察到的地震活动的恢复与假设的乌迪纳火山下方岩浆的位置相关联，指出了恢复火山活动的可能性很高。本研究检查了来自永久地震台站的数据，这些数据显示了地震能量中心从B向南的系统位移。乌迪纳（Udina）从2017年10月至2019年8月。中心表征了产生大量地震活动的体积位置。我们使用了2017年6月7日至2017年9月23日以及2018年5月21日至9月期间从60号轨道下降轨道拍摄的Sentinel-1A卫星图像（波长5.6厘米）（10张图像） 30,2018（12张照片）确定B.Udina斜坡上的时间序列和平均位移速度。持久散射体只能在B.Udina的脚下识别。火山表面位移时间序列分析显示，西南和东部斜坡上2017年和2018年的位移特征几乎保持不变，而西北斜坡上的平均位移率在2018年下降。我们使用了2016年10月4日，2016年6月13日和2018年10月2日从上升轨道拍摄的三张ALOS-2 PALSAR-2卫星图像（波长23.5厘米）来构造成对的干涉图，以表征当时的位移图像之间的时间间隔。除了局限于局部浮雕形式的狭窄区域外，两个干涉图上的位移均不超过几厘米。如此检测到的变形最有可能是由于表面处理。与岩浆室内5 km深度的压力变化相关的变形体积必须具有10–15 km的线性尺寸，而在卫星图像中检测到的位移区域要小得多。这些结果提出了一个替代模型，该模型假定地震活动的恢复伴随着B岩浆熔体的撤退和下沉。