卷 52, 编号 1 (2016)

Using the example of safety provision problems of hydraulic engineering structures (HESs), the seismic monitoring experience is analyzed (parameters of states of objects, equipment and schemes for fulfilling seismic observations) and, based on this, it is proposed to modify existing industrial monitoring practices. The efficiency of the different kinds of the HES monitoring performed by the united seismic equipment with an expanded dynamic range is shown. Innovative instrumental solutions for recording seismic signals are described.

A small-aperture seismic array consisting of seven three-component seismometers carried out continuous measurements of regional seismicity in a selected area of the Nizhni Novgorod nuclear power plant during four months of 2013. Automatic signal detection using beamforming was applied separately for each motion component. Two horizontal components were transformed into radial and transverse components for the given values of the velocity and azimuth of the plane wave front. We have investigated the dependence of the coherence of microseismic noise on frequency, azimuth, and slowness, as well as determining the level of cross-correlation between signals on separate channels in order to estimate expected improvement in the signal-to-noise ratio, which is crucial for signal detection. Most signals detected by the seismic array from regional sources are associated with quarry blasts. Using repetitive explosions at seven quarries, we have quantitatively estimated and compared the increase in detection efficiency of regional seismic phases using a three-component small aperture seismic array and a subarray of vertical sensors. Horizontal sensors showed a higher efficiency in the detection of transverse waves, while the subarray of vertical sensors missed S-waves from certain events. For one of the nearby quarries, the vertical subarray missed up to 25% of events (5 of 20). The results of the investigation point to the need for the use of three-component seismic arrays for the study of regional seismicity.

We propose to use waveform cross correlation techniques for seismic monitoring of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) by proving the ability to build the Global Grid (GG) of master events using high-quality waveform templates at stations of the International Monitoring System. In seismically active regions, the choice of the highest quality and most representative signals from earthquakes as templates for master events is straightforward and one can reduce the current amplitude detection threshold at the International Data Centre (IDC) by a factor of 2 to 3. This gain practically doubles the number of built events, and thus, is crucial for seismic monitoring under the CTBT. However, the coverage by real masters is confined to areas with natural seismicity. Here, we investigate the possibility to populate the GG with real and synthetic master events as a two part study. In Part I, we estimate the effectiveness of cross correlation based on a regular grid filled with grand-master events with replicated high-quality waveform templates.In Part II, we develop and estimate efficiency of synthetic waveform templates for aseismic zones. Both approaches are quantitatively tested using the aftershock sequence of the April 11, 2012 Sumatera earthquake. The cross correlation bulletin previously built using sixteen real master events is a natural benchmark to evaluate the performance of the replicated masters and synthetic waveforms. In Part I, we prove that the replicated grand masters demonstrate the performance at the level of real masters. The Primary IMS Seismic Network includes many array stations, which provide a higher resolution monitoring based on cross correlation.

Equipment for simulation in laboratory conditions of hydrate-containing artificial samples and measuring their acoustic properties (wave velocities, absorption and attenuation) at different temperature and pressures is designed and constructed. The plant consists of a high-pressure chamber (up to 45 MPa), a measuring system intended for the excitation and reception of acoustic waves, systems for temperature and pressure control (axial and lateral) and for gas/liquid delivery into the sample. The measurements are performed on cylindrical samples with a 30-mm diameter and height of 10–50 mm. A set of successful test experiments was performed, including measurements of acoustic velocities of consolidated (plexiglas, sandstone, and frozen sand) and unconsolidated (dry and wet quartz sand) samples and formation of methane-hydrate bearing samples.