Evaluation of the forecast reliability of site effect for regional mining tremors

It is obligatory for Polish underground mines of hard coal and copper to prepare long-term exploitation projects for 2 - 5 years. All the natural hazards, including seismic ones, that may occur have to be taken into account in such projects. In the case of mining seismicity the forecast of site effect plays an important role. To recognize the reliability of this forecast for strong regional mining tremors special methodology was used. The peak ground velocity and peak ground acceleration, recorded after the occurrence of a regional tremor by surface seismometric network stations, were compared with the distribution of the forecast values of these parameters determined for similar seismic energy. Differences between these values are the basis for the evaluation of the reliability of the forecast site effect. The practical implementation was presented with the tremor of seismic energy E = 5.108 J (ML = 3.63) which occurred on 18th January 2018. The small value ΔPGVHmax (4%) of the difference between the recorded PGVHmaxrec and the forecast values PGVHmaxpr confirms that the measurement values correlate well with the forecast values. The difference value ΔPGAH10 for the peak ground acceleration equals 31% showing a worse correlation with the forecast data.

Experimental Data Set of Mining-Induced Seismicity for Studies of Full-Scale Topographic Effects

This paper describes two large, high-quality experimental data sets of ground motions collected with locally dense arrays of seismometers deployed on steep mountainous terrain with varying slope angles and topographic features. These data sets were collected in an area of central-eastern Utah that experiences frequent and predictable mining-induced seismicity as a means to study the effects of topography on small-strain seismic ground motions. The data sets are freely available through the George E. Brown, Jr. Network for Earthquake Engineering Simulation data repository ( NEEShub.org ) under the DOI numbers 10.4231/D34M9199S and 10.4231/D3Z31NN4J. This paper documents the data collection efforts and metadata necessary for utilizing the data sets, as well as the availability of supporting data (e.g., high-resolution digital elevation models). The paper offers a brief summary of analyses conducted on the data sets thus far, in addition to ideas about how these data sets may be used in future studies related to topographic effects and mining seismicity.

Study on Dynamic Disaster in Steeply Deep Rock Mass Condition in Urumchi Coalfield

The possible mining seismicity (MS) and its prediction are important for safety and recovery optimization of mining in steep-heavy-thick rock mass condition. The stress-lever-rotation-effect (SLRE) model of fault-like mobilization was proposed preliminarily. Some innovation monitoring technique approaches for mining seismicity assessment were successfully fulfilled at Wudong Mine of Urumchi Coalfield, China. The characteristics on acoustic-seismic-wave index indicated the spatial-temporal-strength and stress redistribution of steeply deeper-heavy thick coal and rock masses. Applications in field investigations showed that the innovation monitoring (in time and space) of these instruments could provide important information about the performance of mining disturbed structures (heading and steep pillar) during caving of competent overlying roof strata. The prediction and evaluation for mining seismicity were applicable and valid. Operating practice showed that mining efficiency was raised and conspicuous economic benefit was obtained. This approach provides essential data for assessing mining seismicity, coal burst, dynamic hazard prevention, and deep mining potential.

Mechanisms of Mining Seismicity under Large Scale Exploitation with Multikey Strata

The dynamic disasters are aggravating with the increase of exploitation scale and intensity in Chinese coal mines, to further understand this problem, we studied the mechanisms of mining tremors induced by key strata movement and instability under large scale exploitation. First the mechanisms were categorized into two groups that is main key strata fracture and movement as well as subkey strata instability again under adjacent mining activities. Based on the key strata theory in ground control we revealed three basic mechanisms of key strata destabilization that are rotary and sliding of low subkey strata, shear sliding of the high subkey strata, and the main key strata rupture and cave at limit span, respectively. The microseismic observing systems were applied to monitor the mining tremor events and verify the theoretical analysis in different coal mines. The characteristics of time-space evolution of tremors show that low inferior key strata causing the most, followed by the high inferior key strata and the main key strata least, however the released energy was just opposite.