Processing (Trace)

Overview

Click to Enlarge Trace provides tools to derive source parameters from the seismograms recorded by the IMS seismic system. The software is available for Windows and Linux. Interactive functionality includes the picking of phase arrivals in standard or hodogram modes, calculation of the location of earthquakes and source parameters derived from the spectra of seismic waves. These parameters include radiated seismic energy, co-seismic inelastic deformation and magnitude, as well as focal mechanism solutions (time and frequency domain).

Visualisation

Seismograms can be displayed as acceleration, velocity or displacement traces, in standard mode, unrotated modes, polarised modes. Spectra of seismic waves can be analysed to detect noise and adaptively remove it. When integrated with the IMS Visualisation Software, 3D visualisation options become available, making it possible to view the processed events in proper context.

Preprocessing

Click to EnlargeTrace performs removal of 50/60 Hz noise which is commonly induced by a ground loop in mining environments. Baseline corrections, instrument response corrections and anti-aliasing is performed to prepare the seismogram for automatic or manual phase picking and subsequent source parameter calculation.
 
 

Picking Phase Arrivals

Automatic picking of the body wave arrivals can be performed using one of a variety of techniques, including AIC methods, AR methods and phase polarisation methods. P- and S-wave arrivals can be manually picked if the automatic results are not satisfactory or if the highest quality data is required.

Location

In the simplest case, location is performed using apparent velocities which are defined per sensor site, using absolute arrival times or S-P time differences when needed. For complex geology or caving environments, 3D ray-tracing (using a custom-built velocity model) is employed to improve location quality. Usually, a location quality with an error of less than 3% of the average source-site ray path distance is required. Relative location can be employed when good quality events or blasts can be selected as master events.

Source Parameters

phi_plugins_thumbAssuming a far-field radiation pattern for sensor sites sufficiently distant from the hypocenter, a spectral analysis of the waveforms from recorded seismograms allow fitting a standard omega-2 model to the distance-corrected spectra. From this, static source parameters such as seismic potency can be computed. Dynamic parameters such as radiated seismic energy are calculated from energy flux at sensor sites, taking inelastic attenuation and geometric spreading into account. These attenuation parameters can be imposed as fixed parameters, or calculated on-the-fly. From the resulting set of static and dynamic source parameters, we calculate seismic moment, local magnitude, corner frequencies, static and dynamic stress drops, apparent stress drop and apparent volume.

Filtering and Exporting

Various ordering and filtering options are available, making it possible to filter the view of data according to specific source parameter values. It is then possible to export data to text format (so as to use in standard spreadsheet software), or export seismograms to raw ASCII and other formats for external use.

Extensibility

Plugin modules are available from IMS to add certain specialised functionalities to the software, if required. This could include live Wadati plots and various moment/potency tensor solvers. Please contact us for any special requests you may have.

Download IMS Trace here