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Damage to a huge dam can cause great loss of human life and property, but disasters and their consequences can be minimized by implementing effective dam safety monitoring strategies. However, establishing a permanent monitoring system on a huge dam is costly. Additionally, for reasons of national security, many dams and information about them may not be able to be accessed by researchers. Accordingly, continuously monitoring the structural health of a dam by measurement may be difficult. This study presents a way to continuously monitor the health of a dam using vibration signals that are measured not on the dam but close to it. The Sayano-Shushenskaya Dam in Russia is used to demonstrate the idea. Intensive ambient vibration measurements were firstly made once to determine the natural frequencies of the dam. Then the natural frequencies of the dam under varying environmental effects are obtained from the spectra of the seismic records obtained at Cheryomushki seismic station, which is located 4.4 km northeast of the dam. To account for the effects of varying environmental conditions on the natural frequencies, an autoencoder in the form of an unsupervised learning neural network, was employed. The autoencoder was trained using the natural frequencies without using any environmental factors to learn the intrinsic behavior of the dam under varying environmental conditions. The errors between input data to the trained autoencoder and the regenerated data from the autoencoder can be used to determine whether the dam is under normal conditions. A finite element model of the dam was constructed to simulate changes of natural frequencies due to cracks in the dam structure. The results demonstrate that the proposed method can feasibly monitor the structural health of the dam.

The paper describes the effects of the passage of the Chelyabinsk meteoroid (which exploded on 15 February 2013 over the Chelyabinsk Region), which were established from geophysical data from West Siberian stations. The trajectory and speed of the meteoric body from the start of the glow to the breakup were recorded by surveillance cameras and dashcams. Records from broadband seismic stations were used to determine the exact time of the explosion (03:20:34 UTC) from the arrival times of the surface wave produced by this event. The explosion energy was estimated from the surface-wave amplitudes at ~100 kilotons on the assumption that the wave originated from a point source similar to a high-altitude thermonuclear explosion. A database of records from seismic stations obtained during the meteoroid passage has been compiled.

Analysis of geological and geophysical data on the boundary zones between the Eurasian plate and other plates shows poor knowledge of the deep structure of the region. This information will help to refine the position of the plate boundaries and the structure of the Earth’s crust and mantle. We present data on the seismicity and deep structure along the deep seismic sounding (DSS) profile running across the boundary between the Eurasian and Okhotsk plates. A comprehensive analysis of the DSS materials and seismic data shows a significant expression of this boundary zone both in the deep Earth’s crust structures and in the Moho. A zone of anomalous seismicity and deep structure extends along the DSS profile for several hundred kilometers. We have refined the position of the main boundary between the Eurasian and Okhotsk plates, which passes approximately along 144° E.

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