Calculator for designing effective drawpoint bunds.

Energy and moment are two independent measures of the strength of a seismic event. Their physical meaning and how they are calculated was described in a previous post. Analysis of the relationship between the energy and moment of events can provide insight into seismic sources. For example, blasts or ore pass noise, falsely processed as real events, tend to have distinct zones on an energy-moment chart. In general, events with higher-than-average energy are associated with high relative stress.

What do the hazard isos mean?

Why are the event magnitudes different in mXrap?

Log scales and Gutenberg-Richter distributions.

The Grid Based Analysis application can be used to evaluate the spatial distribution of various seismic parameters. There are a range of source parameter options available, and they can give indications to the rock mass behaviour. Some parameters can be considered as a proxy (stand-in) for rock mass stress, while other parameters can be a proxy for the amount of deformation. There are also parameters available that are associated with the rock mass mechanism or event type.

Evaluating the spatial distribution of various seismic parameters.

Overview

The Hazard Assessment application uses a grid-based approach to describe the seismic hazard throughout your mine. Each grid point essentially represents a seismic source with a specific frequency-magnitude relationship. A frequency-magnitude relationship is defined from the $M$, $Mmin$, $b$-value, and event rate. We've previously delved into $M{UL}$ in this post. We also discussed how $Mmin$ and $b$-value are calculated along with other gridding parameters in this post. The event rate is something we haven't taken a dive into yet, so we'll get into it in this post.

The grid-based hazard calculations in the Hazard Assessment app were discussed in a previous post. The Iso View describes the hazard at all locations within the mine but when you are considering the seismic risk for a particular work area, large events and strong ground motions may come from multiple sources. The Excavation View estimates the seismic hazard associated with working areas (minode locations) in a few different ways as described below.

Mine Geometry Model Minode Generator is a new utility app which enables you to generate your own new minodes from a mine geometry model. If you're not sure what minodes are or why you would want to generate them, see What are minodes? If you're not sure what mine geometry models are, see Mine Geometry Models Application.

IMS and ESG sites should have moment tensors loaded in with the events table automatically.

A geotech's guide to understanding moment tensors.

Tools for monitoring drawpoint conditions and inrush events.

Where is the cumulative energy line on the Omori chart?

Dashboard tools for inrush risk reporting and TARPs.

You know that energy and moment are parameters to describe seismic events. But what exactly is their physical meaning for a seismic event source and how are they calculated?

Overview

Probabilistic seismic hazard calculations are dependent on the number of events (N) and the b-value. But which has more effect on the hazard result? The chart below shows how seismic hazard varies with b-value for N = 1,000, N = 10,000 and N = 100,000.

As mentioned in the last blog post, energy and moment are independently calculated based on the displacement and velocity spectra of the recorded waveforms. Another spectral parameter is the corner frequency.

A new window has been added to the Hazard Assessment app (Figure 1). The sensitivity analysis aims to quantify the effect of the variation of the input parameters on the hazard. These analyses can also help the user to determine the optimal settings to use for many of the parameters. This window allows the user to vary only one parameter at the time.

A stochastic declustering algorithm has been implemented in mXrap to separate events into 'clustered' and 'background' components. It can be useful when designing seismic exclusions and re-entry procedures to separate seismicity that occurs in short bursts from seismicity that has low variability in space and time. Short-term exclusions cannot be used to manage the risk associated with background seismicity, since the hazard inside a potential exclusion would be the same as outside the exclusion. Efficient exclusion and re-entry procedures target areas where seismicity is most clustered and where the seismic hazard to which people are exposed can be reduced with a short disruption to production.

The strong ground motion (SGM) relationship is used to calculate the peak particle velocity (PPV) generated by a seismic event. You may also hear this referred to as a ground motion prediction equation (GMPE), but only the maximum velocity is estimated, i.e. the strong ground motion, rather than the full, complex wave motion.

That is the question. An explainer on seismic hazard measurement.

A few new features have been added to the Hazard Assessment application, aiming to improve usability, understanding and investigation. The first addition is a chart in the hazard setup window to indicate the current date range settings. Usually the date range for calculating b-value will be a lot longer than for calculating event rate. Hopefully the chart will be a handy visual aid to help you keep your bearings when setting the hazard analysis periods.

Framework for monitoring and controlling inrush hazards.

MUL refers to the truncating magnitude of the Gutenberg-Richter distribution