New b-value isosurfaces

The isosurfaces for b-value have been upgraded in the latest root. There is now much more control over the isosurface levels. Up to 5 iso’s can be plotted for user defined ranges. A linguistic name can be assigned to each level and displayed in the legend. A new video has been uploaded to the Hazard Assessment page that explains the new b-value isosurfaces.

 

Moment Tensors in General Analysis

Moment tensors have been added to the General Analysis application in the recent update. Beach balls and principal axes can be viewed in the General Analysis 3D view. There is also a separate Moment Tensor window with a number of stereonets and mechanism charts. Two new training videos have been uploaded to the General Analysis page that walkthrough the new tools.

IMS sites should have moment tensors loaded in with the events table automatically. ESG sites can add moment tensors from CSV files in the Events Import app.

 

 

 

Survey Format Converter

A simple utility app has been added to the main root that can be used to export surveys loaded in mXrap. Possible reasons to use this app include:

  • Switch between file formats
  • Export a decimated survey
  • Export a survey with translated or swapped coordinates
  • Combine multiple surveys into a single file

Currently supported export formats are:

  • DXF
  • DTM / STR
  • PNT

A training video for the Survey Format Converter has been added to the General and FAQ page.

NEW Seismic Activity Rate Monitor

The seismic monitoring applications have been modified in the latest root update. There are now two seismic monitoring applications and a third app for setup. The two different monitoring apps are required because not all sites wanted to use exclusion procedures. The monitoring app with exclusions has a different user interface structure and a few extra features.

A new window has been added to monitor activity rate so that both monitoring apps have windows to monitor events and to monitor activity rate. The activity rate monitor is the same in both apps. The Setup app is used to initialise and modify all of these monitoring windows. New training videos for seismic monitoring have been uploaded.

https://mxrap.com/training-videos/monitoring-app/

 

 

Activity rate is monitored on a short-term and medium-term basis. Short and medium-term hotpots are listed in two tables based on pre-defined activity rate thresholds and users can switch between short and medium-term monitoring modes. Each hotspot can be highlighted and there are automatic controls for level plan and longsection views. An alert popup message is triggered when a new hotspot has been detected when there were no hotspots beforehand.

 

 

The following steps are required to setup the activity rate monitor.

1.  Define Grid. Activity rate is assessed based on a grid. Specify the areas in your mine that you want to operate the activity monitor. Note that tighter grid spacings will slow down the calculations and reload speed.

2.  Reference Rate. The reference rate is the basis for the activity monitor thresholds. The reference rate may vary by location since the “normal” activity rate for a particular area will depend on the system sensitivity and rock mass response. Try and select at least a few months of events with consistent data quality and where there has been no major change in mining conditions. Use the time-of-day filter to remove the effects of blasting if desired (see diurnal chart). You can also add an extra factor to the reference activity rate or simply use a constant reference rate across all grid locations.

3.  Monitoring Parameters. You need to specify a radius around each grid point to measure the activity rate and define the time period that constitutes short-term and medium-term activity rate monitoring. You can also specify a minimum number of events to trigger an activity rate caution or alert. You probably don’t want to trigger an alert whenever any event happens.

4.  Activity Thresholds. This is where to define what activity rates will trigger a caution or an alert. You can either specify activity thresholds based on a probability or based on a ratio. Ratio-based activity thresholds are a simple linear function of the reference rate. Probability thresholds are based on the work of Marsan (2003) on detecting seismicity rate changes between two time periods. The P-value refers to the probability that the ratio of the current activity rate to the reference activity rate is greater than the activity ratio (r). If the activity ratio is one, the P-value is simply the probability that the current rate is greater than the reference rate. The probability-based thresholds account for the different uncertainty introduced by using a very short time period (e.g. 30 mins) to assess the activity rate compared to a reference rate measured over a much longer period (e.g. 6 months). For further reading I recommend the Marsan and Wyss (2011) document linked below.

Once you have reviewed all the parameters and thresholds, the settings must be saved before they will be applied to the activity rate monitoring window.

Marsan, D 2003, ‘Triggering of seismicity at short timescales following Californian earthquakes’, J. Geophys. Res., 108(B5), 2266, doi:10.1029/2002JB001946. Available at: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2002JB001946 

Marsan, D & Wyss, M 2011, ‘Seismicity rate changes’, Community Online Resource for Statistical Seismicity Analysis, doi:10.5078/corssa-25837590. Available at: http://www.corssa.org/export/sites/corssa/.galleries/articles-pdf/Marsan-Wyss-2011-CORSSA-Rate-changes.pdf

NEW Short-term Response Analysis Application

Another new app has been added to the Seismic Suite for the general analysis of short-term seismic responses. There are multiple features to analyse the short-term response to different triggers (events or blasts) in time and space. In later versions, this app will replace all of the tools in the previous “Omori Analysis Tools” app but version 1 currently only replaces the old “Response to Blasting” window.

There are two main aspects of the app, the simple response viewer and trigger assessment windows. New training videos have been uploaded for the new app.

https://mxrap.com/training-videos/short-term-response-analysis/

Simple Response Viewer

This window is for the assessment of short-term responses. Triggers must be selected (ticked) from the list and response events for the selected triggers can be assessed with a number of tools.

  • Responses 3D — View the trigger locations and response events within range. Adjust the spheroid controls to include/exclude events related to the trigger. “Nearby events” are events just outside the spatial or temporal range of the trigger.
  • Time after Trigger — Chart the events as a function of time after trigger. Can plot events as a histogram or cumulatively. The time bin used for the histogram can be adjusted. When multiple triggers have been selected, can either view responses individually or stacked together. The best fit Modified Omori Law (MOL) is calculated automatically, if the calculation fails a message will appear in the control panel. You can override the MOL parameters (p, K and c) in the control panel. 
  • Distance from Trigger — Chart the events as a function of distance to trigger. Options for X distance, Y distance, Z distance, Horizontal distance and 3D distance. You can normalise the chart by the number of events or by the volume under consideration. Normalisation by number of events changes the Y axis to a percentage of events from 0-100%. Normalisation by volume changes the X axis so that the volume increases linearly as the distance increases (expanding sphere). If the cumulative events is linear for the chart normalised by volume, this represents a constant event density.
  • Density 2D — View the distribution of events in the 2D plane (XY, XZ or YZ). Events are divided into spatial bins and then ranked from highest to lowest density. The grid points are coloured by cumulative events, where the accumulation is from highest to lowest density points. 
  • Density 3D — Similar to the Density 2D plot, uses the same grid spacing controls. Isosurfaces are used to show the cumulative events distribution in 3D. 

Trigger Assessment Window

 This window is for the analysis of triggers; either blasts, events or user defined points in space and time. If the response viewer is to assess the area of exclusion and time of re-entry, the trigger assessment window is to assess which blasts should have an exclusion and which events should have an evacuation.

  • Triggers 3D — View triggers in 3D and use the marker style colours and scales to assess the location of triggers that typically have a response. 
  • Trigger Summary Tables — These tables summarise triggers by various characteristics. For example, you can use these tables to assess what type of blasts have the biggest response, what magnitude events typically have aftershocks, how the responses to triggers vary by depth etc. The tables currently use the following parameters to assess potential triggers for exclusion or evacuation:
    • Blast tonnes
    • Blast type
    • Trigger date
    • Trigger elevation
    • Event magnitude
    • Location (VSA)

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