Acoustic Emission/Seismicity at Depth Beneath an Artificial Lake after the 2011 Tohoku Earthquake

Abstract

Acoustic emission (AE)/seismicity activity increased near the city of Sendai, Japan, after the 11 March 2011 Tohoku earthquake in a newly seismically active region near the Nagamachi-Rifu fault, which caused a magnitude 5.0 earthquake in 1998. The source of this activity was around 12 km beneath an artificial lake. At the same time, activity on the Nagamachi-Rifu fault nearly ceased. More than 1550 micro-earthquakes were observed between 11 March 2011 and 1 August 2012, of which 63% exhibited similar waveforms and defined 64 multiplets. It appears that crustal extension of about 2 m during the Tohoku earthquake and additional extension of about 1 m during the following year changed the stress field in this region, thus generating micro-earthquakes and controlling their frequency. However, it has been presumed that crustal movement during the Tohoku earthquake did not affect the direction of principal stress, and that these events induced repeated quasi-static slips at asperities and the resultant micro-earthquakes.

Structural Health Monitoring of Large Structures Using Acoustic Emission–Case Histories

“…Of these, underground repositories for nuclear waste are especially significant, and millimeter-size defects were located in a million cubic meter volume, demonstrating in situ AE monitoring is a useful tool to observe instabilities in rock long before any damage becomes visible. Moriya [8] presented the use of an AE method for determining the seismicity of a lake bottom following the massive 2011 Tohoku earthquake. Another review by Behnia et al [9] discussed AE methods for evaluating the structural integrity of asphalt pavements located in cold regions.…”