Enigmatic very low-frequency tremors beneath the Shonai plain in northeastern Japan
Enigmatic very low-frequency tremors beneath the Shonai plain in northeastern Japan
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日本东北部庄内平原下方神秘的极低频震动
DOI：
10.1029/2012jb009258
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
K. Nishida and K. Shiomi
中科院分区：
文献类型：
--
作者：
Wada;K.;et al;道上達広;F. Takahashi;K. Nishida and K. Shiomi
最近，密集而灵敏的现代地震台网揭示了构造和火山震动。虽然大多数地震研究都集中在这两种类型的地震上，但也存在其他类型的地震活动。为了检测这种震动活动，我们分析了2004年6月至2006年6月期间Hi-Net高灵敏度加速度计(倾斜仪)的数据。结果表明，日本东北部Shonai平原下存在典型频率为0.085赫兹的甚低频乐夫波地震。地震活动持续数日，冬季每月发生数次。这一活动是由次生微震触发的，次生微震为当地的海洋膨胀活动提供了一个指标。一个可能的来源是沉积层底部的次水平裂缝和流体储集层。所有观测到的特征表明，水文现象是甚低频震颤的潜在来源。由于即使在构造和火山活动不活跃的地区也可能出现类似的水文现象，现代宽带地震仪阵列观测可能会在这些地区发现类似的水文震动。
Recently, dense and sensitive modern seismic networks have revealed tectonic and volcanic tremors. Although most studies of seismic tremors focused on these two types, other types of tremor activities also exist. To detect such tremor activities, we analyzed data from the Hi‐net high‐sensitivity accelerometers (tiltmeters) between June 2004 and June 2006. The results elucidate very low frequency (VLF) Love wave tremors with a typical frequency of 0.085 Hz beneath the Shonai Plain in northeastern Japan. The tremor activity lasted for several days and occurred several times per month in winter. The activity was triggered by secondary microseisms, which provide a proxy for local ocean swell activity. A possible source is a subhorizontal crack coupled with a fluid reservoir at the bottom of the sedimentary layer. All the observed features suggest that hydrologic phenomena are potential sources of VLF tremors. Because similar hydrologic phenomena can be expected even in tectonically and volcanically inactive regions, modern array observations by broadband seismometers may reveal similar hydrologic tremors in such regions.