10 docs tagged with "Theory"

Why are the event magnitudes different in mXrap?

When you are using the frequency-magnitude chart, it can be easy to forget it is log scale and this can distort a few things. Consider the chart below; have you ever thought the Gutenberg-Richter distribution doesn't look right? Think it isn't matching the large events very well?

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.

Background filters

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.

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.

Where is the cumulative energy line on the Omori chart?

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?

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.

As mentioned in the last blog post, 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.