Hazard Assessment – Event Rate

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 MUL, Mmin, b-value, and event rate. We’ve previously delved into MUL 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. Event rate sounds like a simple calculation but there are quite a few complexities worth explaining here. There are also a couple of controls for event rate hidden away in the Advanced Tools that might be worth investigating at your site. These controls will be explained below too. The event rate refers to the number of events above a certain reference magnitude, usually Mmin. On the frequency-magnitude chart, essentially the b-value is the slope and event rate is the intercept. It is related to the a-value of the Gutenberg-Richter distribution. You might also see the event rate referred to as the lambda (λ) value. This comes from the Poisson distribution where λ is the rate parameter. The event rate parameter refers to a specific time interval and volume. The number of events during the data period is adjusted to refer to one year’s worth of activity. For the hazard calculations, the event rate is associated with the number of events within the 3D cubic volume of the grid cell. However, the event rate that is plotted in 3D with isosurfaces is adjusted to refer to the event rate within a 50 m spherical volume. The standard volume adjustment is done so that you can modify the grid spacing and the event rate will remain the same. Event Splattering Events within the data period are assigned to the grid with a ‘splattering’ process. Just like if you throw a ripe tomato, it might splatter onto the wall, events are splattered onto its nearby grid points. The kernel function controls the distribution of an event onto the grid. Grid cells closer to the event have a higher weighting. A cubic kernel function is used to assign a portion of each event to grid points within a maximum radius, Rmax. The total contribution of a single event to the grid is always normalised to be equal to one. This avoids the problem of overcounting or undercounting events and ending up with an inaccurate grid event count. If you have 1,000 events in the data period, you want the total event count of the grid points to also work out to 1,000. When all events have been splattered, each grid point then has the number of events associated with its cubic volume. The maximum radius, Rmax, of the kernel function is adjusted for each event. Larger magnitude events have a bigger area of influence. The radius is also expanded in lower density areas to reduce the artifacts around the edges of seismic clusters. The Rmax is generally the maximum of the following parameters: 20 m. Minimum Rmax for all events. 1.5 x Grid Spacing. To avoid events missing grid points when grid spacing is large. Event Source Radius. To increase the zone of influence of large events. Distance to the 5th Nearest Event. To smooth areas with sparse event density. These parameters are capped at 100 m so Rmax can’t go higher than that. There is a final smoothing factor applied to Rmax that is a control in the Advanced window. The default smoothing factor is to double the calculated Rmax. The figure below shows the effect of the smoothing factor on event rate at the Tasmania mine. Increasing the smoothing factor generally lowers the peaks and raises the troughs of the event rate distribution throughout the mine. Small Event Weighting Event rate calculations generally use events above the global Mmin. The trouble is this excludes a significant portion of the database and limits the resolution of the seismic hazard assessment. To try and utilise additional data, events just below the global Mmin are also considered. Events below Mmin within a magnitude range, Δ, are splattered onto the grid as an alternate estimation of event rate. Since these events are under recorded, their contribution onto the grid is increased to compensate. The figure below shows how the small event weighting is calculated by estimating the amount of under recording compared to a complete dataset. The two event rate calculations, from events above the global Mmin, and smaller events, are compared and the higher of the two rates is used. The use of smaller events is turned on by default, but you can turn this off in the Advanced window. You can see the difference in the event rate calculations at the Tasmania mine with and without the small events. The differences are small but there is generally more information at the edges of the seismic clusters when small events are used. Using Local Mmin The event rate calculations generally don’t consider the spatial variation in Mmin. However, we have made a recent addition to give you the option of using the local Mmin calculated at each grid point. The same approach is taken, except an event is only splattered onto a grid point if its’ magnitude is above the local Mmin. The small event adjustment still works but the global trend in under recording is used for the small event weightings. The local Mmin option is available in the Advanced window and the results are compared for the Tasmania mine below. The same general trends are there when using local Mmin although it does increase the variability. The differences are more prevalent in areas with lots of data. Concluding remarks Feel free to investigate these event rate controls at your site and consider if they might be of use to you. In general, the differences will be small as the event rate is fairly insensitive to

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Inspections and data entry app

We are excited to announce our new inspections and data entry app. This app is a general purpose data entry app designed for offline use with tablet devices which can be customised to fit each site’s exact needs.The app allows simple and fast input of multiple data types (selection, text, numerical inputs, orientation etc.) as well as attaching photos and sketches to reports. Inputs can be grouped into sections, or into different pages for easier use. The location of inspections can be georeferenced using the mineplans and a polyline system to show where the inspection was done. Data can also be attached to this polyline, to indicate different data in different areas. An example of this is rock mass characterisation mapping, where different sections of drive can be assigned values. The app also allows you to view the data from previous reports. This view can also be saved as a PDF file to use as a report that can be given to management etc. The desktop mXrap side of the app is also completely customisable, and the mXrap team can help you to build exactly what you want to achieve the analysis you need to do. Tables with inspections registers, charts for monthly reports, 3D views to show the underground locations of inspections and even automatically generated reports. Uses of the app so far include:– General underground inspections– Quality Assurance/Quality Control inspection– Rock mass Characterisation mapping– Open Pit Inspections– Pastefill UCS Testing If you want more information or are interested in trying in the app, please get in contact with the mXrap team via

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Export Panel for 3D Views, Charts and Tables

The export panel, located on the right-hand side of 3D views, charts and tables, can be used to generate images, files, and videos with just a couple of clicks. This panel is particularly useful for preparing presentations and papers that require figures with specific dimensions or font sizes. Use the ‘Export dims:’ functions to create high quality images of a specific size: Use the ‘Content:’ options to change what components are shown: Export tables to the clipboard or as a file: Create custom videos of your data, analysis and results: For a more detailed walk through of how to use the export panel, check out the mXrap training video:

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mXrap Version 6 – User Change Logs

We’re pleased to announce the release of mXrap version 6, bringing with it a range of enhancements to elevate your mXrap experience. This major update includes improvements to the user interface, as well as enhancements to speed when loading the root folder and applications. Additionally, we’ve upgraded the 3D rendering and navigation capabilities in the 3D views. However, it’s important to note that older root folders may not function properly in version 6 due to incompatibilities. Therefore, it’s crucial that all root folders and apps are upgraded and checked to ensure they work correctly before transitioning. If you haven’t received communication about this upgrade yet, expect an email in the coming weeks with instructions on how to complete the process. Please be aware that mXrap version 5 is scheduled to cease functioning in May 2024. Your cooperation during this transition period is greatly appreciated and will help facilitate a smooth migration to the new version. When you transition to version 6, you’ll need to rebuild your event survey caches. If you require assistance with this or encounter any other issues, please don’t hesitate to contact us at our support email address. For a comprehensive list of changes, please refer to the user change log here: mXrap Version 6.0.0 User Change Log For developers actively working on applications within mXrap, additional information can be found here: mXrap Version 6.0.0 Developer Change Logs We’re excited about the possibilities that version 6 brings and look forward to your continued support and feedback.

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Modifying The Blast Record

When trying to add, delete or change blasts in mXrap, best practice is to use the ‘Blasts Editor’ found under the ‘General Set-Up Windows’ tab: If you need to make bulk changes however, it may be tempting to directly alter the input file in the root folder. Problem: When you open the ‘Blasts.csv’ in MS Excel, it automatically changes the date format and mXrap is no longer able to read the blast information. Solution: Prior to saving the new file, format the Date column to match the input required for your root: yyyy-mm-dd hh:mm:ss.0   This is the typical input format, but you may have to modify slightly in order to match the format for your specific root. This can be done by selecting the Date column, right clicking, and opening ‘Format Cells’. Choose the ‘Custom’ category, and manually enter the input format for your root: To see your changes, save the file and ‘Reload Data’ in mXrap.

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RMDA app: new geotechnical domains delimiter app and more!

A new app has appeared in the Rock Mass Data Analyser suite: the Geotechnical Domains Delimiter. This app allows you to create your own geotechnical domains; either from boundaries (e.g. lithological contacts or fault planes) or volumes (e.g. lithologies, domains, selection boxes). The app uses the HW/FW filter to classify the space in relation to each survey imported (inside a survey = ‘ore’; hanging wall = hang; footwall = foot). Each unique fingerprint combination is represented by a point (see pink dots in Figure 2). To identify key areas, these points need to be assigned as a ‘reference point’ by giving it a name (Figure 2). Afterwards, geotechnical domains names can be assigned to the defined reference points (Figure 3). A single geotechnical domain may have multiple fingerprints, thus it needs to be defined by more than one reference point. In this example, most of the geotechnical domains were associated with two fingerprints each. The geotechnical domains created automatically classify all the data in the Rock Mass Data Analyser: the rock mass quality data (e.g. RQD, G, RMR, GSI), the structures, the geology observed in borehole segments, stress measurements etc. Figure 4 shows the lab tests, the rock mass quality intervals along boreholes and stress measurements in Region2 with ticks in the Filter panel. For more information, view the five training videos detailing the Geotechnical Domains Delimiter app. Borehole ID: more flexibility to show text in 3D For all borehole sources, you now have the ability to show the borehole ID along the dip of the hole and at the top or bottom. To do so, the controls of the text series related to the borehole IDs must be adjusted (see Figure 5). If more than 1,000 boreholes need to be displayed, do not forget to increase the ‘Max # to plot’ field! Detailed data errors There is now a detailed error panel of the data imported and saved for all data sources (rock mass quality, structures, lab tests etc.). These panels detail the boreholes or sample for which the data is outside the expected range, the concerned parameter, and its value. A table summarising all the rows containing ‘bad quality data’ is available in Rock Mass Data Analyser. The values outside expected ranges are clearly highlighted in red. The segments containing ‘bad quality’ data can also be seen in 3D space (Figure 6). The ‘good data’ table only shows the data used for calculations; if a sample/borehole interval contained a ‘bad value’ for a parameter, only that parameter is ignored in the calculations, not the entire data for the segment/sample. Rock mass quality data: using RQD from another source New features in the Rock Mass Data Importer/Analyser allow you to import RQD values with intervals other than the one defined with your rock mass quality data csv. The first step is to import the csv containing the RQD data along the borehole, in the following column order: Borehole ID, From, To, RQD value (see Figure 7). Afterwards, the newly imported RQD values can be seen alongside the RQD values from your rock mass quality data imported, if it exists. You can choose which RQD values to use for the further analysis (Tables, Charts & 3D View) in ‘Select RQD sources’ (see Figure 8). The same panel can be found in both the Rock Mass Data Importer app and the Rock Mass Data Analyser app. Do not hesitate to contact the mXrap support team for an app upgrade to get all these features!

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Sensitivity Analysis in Hazard Assessment app

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. The steps to realize such a sensitivity analysis are quite simple (Figure 2). All the input parameters that can be studied are: Examples presented are from the Tasmania root and expressed a sensitivity analysis for the grid spacing. Annualised probability The following hazard calculations all refer to the annualized hazard and apply to the entire volume of the chosen grid: The overall variation for the three main hazard assessment are shown in Figure 3. Grid-based Hazard (Hazard Iso’s window) 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. Details on hazard Iso’s can be found in the blog post:   For the grid-based hazard, the distribution of parameters listed in Table 1 can be investigated. The distribution refers to the value for each grid point composing the volume studied, for which the grid extent and spacing are set. Hazard Parameters Other Parameters ML Rating:   Seismic Rateb-value MminKS Frequency-Magnitude relation Table 1 – Parameters for which the impact of parameter input variation are studied The ML Rating is the design magnitude that would have a probability of exceedance of 15%. The ML Rating Isossurface can be visualised in the 3D view for each ML Rating Level ticked for each step (Figure 4). Hazard on excavations The Excavation View estimates the seismic hazard associated with working areas (minode locations) in a few different ways. More details can be found on blog post : The effect of the input parameters variations can be visualised on the hazard on excavation, expressed by the P [ML within R] and P [PPV > PPVDESIGN]. The distribution of both parameters for each minode can be seen for each step (Figure 5).

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Updates to Short-term Response Analysis

There have been a number of recent updates to the Short-term Response Analysis app. These include: Chart for determining re-entry using different parameters: This chart gives you values for a particular parameter over time (based on a user-defined time window size and step). A threshold value for that parameter can be set, allowing you to see when the seismic data drops below that threshold. The parameter investigated can currently be set to energy, event count, hazard, background ratio and activity rate probability. For more information about these parameters, see Tierney et al. 2019.   Frequency–magnitude and log energy–log moment charts for response events: This allows you to do more detailed analysis of responses, to try to understand the underlying mechanism of the response and the distribution of events.  Time versus distance to trigger chart: This allows you to investigate whether there are trends in your response seismicity dependent on the distance from the trigger.  Trigger distributions chart: This is for allowing you to analyse the distribution of selected triggers, to help you make better decisions as to what criteria to use for re-entry and at what level that criteria should be set    Charts for analysing cumulative distributions of parameters: This is for allowing you to see the full distribution of seismic event parameters for a trigger (or multiple selected triggers). The parameter investigated can currently be set to cumulative number of events, cumulative moment, cumulative apparent volume, activity rate, energy index, apparent stress frequency and b-value.   If you need a root upgrade to see these charts or have any questions on their use, please contact the support email address for help.

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HW–FW filter

For a few months now, a new tool has appeared in the General Analysis app; the hanging wall (HW) and footwall (FW) filter. The HW–FW filter allows you to filter your events based on where they are in relation to ticked survey/s. If more than one survey or plane is used for the HW–FW filter, they need to be somewhat parallel in order to make sense. Below is an example of the classification when one survey (FIG 1) and two surveys (FIG 2) are used. The events are categorised into four categories, which can be visualised one at a time or simultaneously:  If mXrap does not use the terms hanging wall and footwall correctly, there is the option to ‘flip’ it. By default, the events are classified using a plane orientation that is automatically determined by averaging the orientation of the triangles in the input survey/s. It is also possible for you to specify the overall plane orientation (dip and dip direction) used in calculations, which may be useful if the automatically determined orientation does not match your expectations. The change of the overall plane orientation will affect the event’s classification (FIG 3). The events are unclassified if they are outside the boundaries of the survey, or if there is a ‘hole’ in the survey. There is the possibility to classify the unclassified events under HW, FW and ore by ticking ‘using nearest vertex instead’. Examples of how the events are classified for the earlier example using the ‘classify outer events by nearest vertex’ way is shown (FIG 4). The volumes created by the HW–FW filter can be saved. A volume will be created for each classification (HW, FW, ore, unclassified) with the defined name, which could be the name of the survey/s used for the classification. These volumes will automatically appear in the VSA table (FIG 5). If your surveys have dense mesh, consider using the ‘simplify mesh’ option as it will speed up the calculations process for the exported filter volumes. For now, these filters are used for events. However, the same tool can be applied to other data. That classification tool can be used with multiple surveys simultaneously. It can further be applied to different data types, such as structures, rock mass classification or intact rock tests. Stay tuned for further tips and training!

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What are Bundles?

Bundles are a form of protection which we use to limit access to specific parts of mXrap applications. One of the primary incentives behind the use of Bundles is to reduce the amount of the root folder which is exposed to users for editing. While we encourage users to modify the root folder to suit their specific needs, modifications to core parts of the app can hamper our ability to maintain and upgrade root folders efficiently. Bundles provide us with the flexibility to prevent users from editing important parts of the app while leaving other parts accessible for customisation. This helps us to deliver and upgrade bundled apps much more reliably. Bundles can also be used to provide protection of mXrap’s and other developers’ intellectual property (IP). By being able to lock down important parts of the code using Bundles, it allows us to distribute mXrap to a wider audience without worrying about sensitive IP being exposed. In addition, access to Bundles in mXrap is tied to a user’s license key by a Bundle License ID. This feature allows us to ensure apps are only accessed by the permitted users and cannot be freely distributed. We have begun to roll out the Bundles in two stages. Stage one is to lock everything down and see what no longer works. Stage two involves opening back up again as required. If you encounter limited access to a tool which you believe would be beneficial to either use, view or customise please email us at using the support email. Developer notes – how it works: Bundle settings are defined by a permission file called _mxbundle.mxperms which is stored in each folder. The permission file also affects each subfolder. If there is a new permission file it will override its parent’s settings.The format for a permission file is:      LicenceId, Access, Export     NUM, ACCESS, EXPORT     NUM, ACCESS, EXPORT Where NUM is the Bundle License ID that should be allowed access.ACCESS is either: none, secret, hidden, visible, editable or overridable.EXPORT is either: internal or exported.Different Bundle Licence IDs can be assigned different permissions by adding multiple lines.The behaviour of the different combinations is summarised below. If you are an mXrap app developer and are interested in bundling your own application please contact us at the support email address.

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