Abstract

This paper studies the characteristics of seismic coda waves attenuation in Caucasus. Short-period coda waves are analyzed from about 500 earthquakes that occurred in Caucasus between 1989 and 2020. The triaxial digital records of seismic events with M ≥ 4.0 recorded at epicentral distances of 120–600 km are used. S-wave attenuation was estimated from short-period coda waves envelopes at a frequency of ~1 Hz. The structural features of the S-wave attenuation field in the upper mantle of the Caucasus are similar to those for other seismoactive zones. The attenuation field is represented by blocks, which have weak attenuation and are subisometric in plan view, and by strong attenuation zones. In the case of blocks, attenuation decreases in the direction from the boundaries to the central of these blocks (Q factor is up to 300–1000). Sources of the strongest earthquakes in the region with M > 6.5 are confined to the block boundaries. The detailed structure of the attenuation field in the aftershock zones of the 1970 Dagestan, 1988 Spitak and 1991 Racha earthquakes is considered. The results agree with existing ideas on the focal mechanisms of these earthquakes. The structure of the attenuation field corresponds to velocity anomalies, magnetotelluric and microseismic sounding results, and thermal field anomalies.

中文翻译：

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利用短周期Coda方法研究高加索地区S波衰减场的一些结果

摘要

本文研究了高加索地区地震尾波衰减特征。短周期的尾波是从发生在高加索地区1989年到2020年间的地震事件的三轴数字记录约500地震的分析中号≥4.0记录在120-600公里，震中距被使用。从短周期的尾波包络以约1 Hz的频率估计S波衰减。S的结构特点高加索上地幔的波衰减场与其他地震活动带的衰减场相似。衰减场由在平面图中具有弱衰减且在等轴测图中的方框表示，并由强衰减区表示。在块的情况下，衰减从这些块的边界到中心的方向减小（Q因子最大为300–1000）。M地区地震最强烈的来源> 6.5限于块边界。考虑了1970年达吉斯坦，1988年Spitak和1991年Racha地震余震区衰减场的详细结构。结果与关于这些地震的震源机制的现有观点一致。衰减场的结构对应于速度异常，大地电磁和微地震探测结果以及热场异常。