Aleksander J. Mendecki

Institute of Mine Seismology · Australia, South Africa

Quantitative description of a seismic event Mining excavations, whether underground or open cast, induce elastic (reversible) and then inelastic (irreversible) deformation within the surrounding rock. Elastic deformation is defined as a process during which no new microdefects are nucleated while all existing microdefects convect with the mass with...

A simple ground motion prediction equation (GMPE) is developed for peak ground velocity, PGV, and for cumulative absolute displacement, CAD, for underground mines. Assuming the ground velocity at source, PGV0=0.63vSΔϵ where vS is S-wave velocity and Δϵ is the average strain change at seismic sources (Brune in J Geophys Res 75(26):4997–5009, 1970; K...

S U M M A R Y We present a thermodynamically based formulation for modelling dynamic rupture processes in the brittle crust using a continuum damage-breakage rheology. The model combines aspects of a continuum viscoelastic damage framework for brittle solids with a continuum breakage mechanics for granular flow within dynamically generated slip zon...

The Mine Seismology Reference Book book grew from the paper "Mine Seismology: Glossary of Selected Terms", which was published in 2013 in the Proceedings of the 8th International Symposium on Rockbursts and Seismicity in Mines. The idea behind the Glossary was to serve both as quick reference material and as a primer on selected terms used in mine...

The potency and energy range of seismic events that a system can recover is limited by its frequency range (f1; f2), which is mainly determined by the capabilities of seismic sensors. In hard rock with vS = 3.6 km/s and rigidity = 30 GPa the largest event for which we can recover 85% of seismic potency is P = 7.41*(stress drop)/(10*f1)^3, which for...

Despite its limitations the power law size distribution hazard estimates offers obvious benefits. It provides a useful association between its parameters and seismic hazard related factors. The �-value correlates positively with the stiffness of the system, with rock mass and mine layout heterogeneities, with the predictability of larger events and...

Despite its limitations the power law size distribution hazard estimates offers obvious benefits. It provides a useful association between its parameters and seismic hazard related factors. The �-value correlates positively with the stiffness of the system, with rock mass and mine layout heterogeneities, with the predictability of larger events and...

This compilation is intended to serve both as reference material and as a primer on selected terms used in mine seismology. The alphabetical ordering has been sacrificed in favour of a more intuitive association among various entries. For the most part commonly accepted symbols are reserved for certain types of variables, but the diversity of subje...

As for earthquakes, the sizes of seismic events induced by mining are, within a certain range, power law distributed: N (� R) = �R􀀀�, where N (� R) is the number of events not smaller than R, as measured by seismic potency P, moment M or radiated energy E, � measures the activity rate and � is the exponent, or the �-value. We analysed different dat...

Unlike earthquakes, seismic rock mass response to mining can be controlled. Seismic hazard in mines is driven by the volume and the spatial and temporal distribution of rock extraction. To forecast seismic hazard for a given mine layout we need to extrapolate its parameters in the volume mined domain rather than in time. It is difficult to reconcil...

Seismic rock mass response to mining is somewhat different than processes leading to and resulting from tectonic earthquakes. The seismicity observed in mines is driven by extraction of rocks rather then tectonic forces. Loading is faster and an interaction of seismic sources with openings and blasting create a variety of source mechanisms. amage i...

Probabilistic seismic hazard estimates depend on the parameters of the survival function that describes the size distribution of seismicity: a, b and Pmax, and on the ground motion relation for a given volume of rock. Parameter a measures the activity rate, b is inversely proportional to the observed mean event size, and the Pmax is the maximum exp...

In 2002, at the Mponeng Mine, South Africa, the Research Group for the Semi-controlled Earthquake- generation Experiments in South African Deep Gold Mines started the observation aimed for monitoring the entire life span of an earthquake. Around our site, the Pretorius fault zone, a length of several km, offsets a gold reef. Within the fault zone,...

The Research Group for Semi-controlled Earthquake-generation Experiments in South African deep gold mines (SeeSA) has continuously monitored strain changes with a resolution of 24 bit 25 Hz at the Bambanani mine near Welkom. An Ishii borehole strainmeter was installed at a depth of 2.4 km near the potential M ~ 3 earthquake source area. Instantaneo...

Mining is not a spontaneous process. It induces stresses in the rock mass at a particular place, at a particular time and at a particular rate, influencing the development of spatial and temporal correlations and interfering with the act of self-organization. Some particular mining scenarios may therefore generate more favorable short term seismic...

Mining takes place at depths of 2-3 km in South Africa, thereby inducing events with M \textgreater 3 in the close vicinity of stopes, with the largest events so far recorded being M \textgreater 5. As a result, seismogenic processes can be monitored at very short distances with sensors installed ahead of time in seismogenic areas. We refer to this...

To study the preparation process of an earthquake, we should get closer to the hypocentre. In co-operation with ISS International, we had an experimental field (∼200 m × ∼200 m) without dykes and faults in a South African deep gold mine. We have monitored more than 20,000 seismic events (M<2) with borehole tri-axial accelerometers. We used a data a...

Understanding and thus modelling of reality means the ability to explain observations. The usefulness of numerical models is measured by the quality of their predictions. It is demonstrated that quality data and proper quantification of seismic sources facilitates better understanding of fundamental processes associated with seismic deformation, e....

We present aspects of one of several ongoing case studies used in the development of prediction techniques for major seismic instabilities. The current investigation centres on accelerated coseismic deformation described by the kinematics of failure and on softening, as well as the characterization of areas of interest by measures of the seismic re...

Today, technology and techniques of monitoring seismic rockmass response to mining allow one to quantilatively analyse hundreds of seismic events, with 'well-behaved' waveforms, per shift and 10 quantify seismicity by arameters relating to change in strain, stress or rheology of seismic deformation. It is proposed that the imminence of potential ro...

The objective of this paper is to quantify the spatio-temporal correlation of seismic events. specifically to test for the localization and orientation of interactive events before failure. The oblateness of the covariance matrix of the correlation length within the correlation time is used as a measure of localization while me eigenvectors of that...

The location of seismic events is of fundamental importance, since all subsequent seismological processing depends, to some degree, upon the event position and the distances to the stations. Finding the location of a seismic event amounts to solving an inverse problem — a set of unknowns has to be retrieved from a set of data. The four unknowns con...

Seismic sensors are distributed around or throughout the volume of interest. The monitoring system must accurately record the amplitude and timing of any significant ground motion over a wide range of amplitudes, frequencies and durations, and assemble the records at a central point for processing, within a reasonably short time so that action may...

The transducer is the key element of any seismic monitoring system. Once the ground motion is transformed into an electrical signal by the transducer, the rest of the system is simply a problem of calibration and data acquisition.

Spectral analysis, i.e. estimation of the frequency representation of time series, usually employs the fast Fourier transform (FFT) algorithm to perform a Fourier transform. This approach to spectral analysis is computationally efficient and produces reasonable results for a large class of signals. There are, however, several inherent performance l...

Routine seismic monitoring in mines was introduced over 30 years ago with two main objectives in mind: • immediate location of larger seIsmIC events to guide rescue operations; • prediction of large rockmass instabilities. The first objective was achieved fairly quickly, but with the subsequent development of mine communication systems, its strateg...

Mining excavations, whether underground or open cast, induce elastic (reversible) and then inelastic (irreversible) deformation within the surrounding rock. Elastic deformation is defined as a process during which no new microdefects are nucleated while all existing microdefects convect with the mass without growing in size (Krajcinovic and Mastilo...

The success rate with the location of seismic events and the inversion of seismic source parameters depends to a great degree on the accuracy of reconstructing the ray paths which seismic waves follow in a given geological medium. In particular, tangents to the seismic rays at the source and at the stations are of importance if routine inversions o...

Nonlinearity and chaos are common features of many systems in nature, (Gutzwiller, 1991; Radu, 1995) though this has been acknowledged largely only during the past two decades. The phenomenon which goes under the name ‘chaos’ is an intrinsic feature of dynamics and comprises the large sensitivity to initial conditions of the evolution of a nonlinea...

Seismic tomographic imaging is the generation of maps of the spatial variation in a seismic parameter through a rockmass. Several seismic parameters may be imaged, such as attenuation or velocity, although P wave velocity images are most common because of the relative simplicity and accuracy of the measurement. P wave velocity images may be constru...

The development of the technology and the appropriate theory of quantitative seismology allows applications far beyond the aims of the first seismic monitoring in mines when hypocentre location and some kind of magnitude determination was considered satisfactory.

The paper describes the concept of quantitative, real time seismology in mines and an example of a specific implementation. Aseismic event is considered to be described quantitatively when, apart from Its timing and location, at least (WO independent parameters penainina to the seIsmic source, e.g. seismic moment and radiated seismic energy or seis...

In the present study, a method is proposed method to estimate strong ground motion from possible large events. The method was demonstrated in two ways. Firstly, the magnitude of ground motion was estimated at distances away from a vertical source. If a worst case event is assumed, the simulation can be used to calculate the resulting ground velocit...

The factors affecting the accuracy of the location of seismic events are discussed. Based on different models of the propagation of seismic waves in the rock mass, several algorithms have been elaborated and presented. In addition to the location of seismic events, these algorithms enable also the parameters of assumed models to be determined. Refs...

Routine seismic monitoring in mines enables the quantification of exposure to seismicity and provides a logistical tool to guide the effort into the prevention and control of, and alerts to, potential rock mass instabilities that could result in rock bursts. One can define the fol-lowing five specific objectives of monitoring the seismic response o...

This report discusses the routine seismic monitoring mechanism which was introduced in mines over 30 years ago with two major objectives in mind: to locate major seismic events and thus guide rescue operations and to detect potentials instabilities.

Numerical modelling of rock-mass response to underground excavations is of vital importance for the decision-making process in designing and running a mine. Likewise, seismic monitoring with state-of-the-art local seismic systems is indispensable as a means for quantifying hazard and as an indicator for potential instabilities in the rock-mass due...