Page History

...

Application objectives
Anthropogenic seismicity rate and magnitude are analyzed using superposed epoch to extract mean field patterns that are more robust than a single series. This application analyses aftershock sequences in the 1-3L near field distances from the "reservoir". L is a proxy for geo-resource dimension, being mine gallery width, reservoir length, etc.
Input data are time series from the seismic catalog.
This application is important to quantify the mean field pattern of several aftershocks that should be compared with regional tectonic patterns.
Outputs as aftershock rate over time may be compared to outputs of application "Earthquake interactions - mainshock scale".
References:
Tahir, M., J.-R. Grasso, and D. Amorese (2012): The largest aftershock: How strong, how far away, how delayed? Geophys. Res. Lett., 39, L04301, doi:10.1029/2011GL050604.
Tahir, M., and J-R Grasso, (2015):"Faulting style controls for the space–time aftershock patterns." Bulletin of the Seismological Society of America 105.5 2480-2497.
De Arcangelis, L., Godano, C., Grasso JR., and E. Lippiello, (2016): Statistical physics approach to earthquake occurrence and forecasting, Physic Reports, 628, 1-91.
Zaliapin, I., and Ben‐Zion, Y. (2016): Discriminating characteristics of tectonic and human‐induced seismicity, Bulletin of the Seismological Society of America, 106(3), 846-859.
Grasso, J. R., Karimov, A., Amorese, D., Sue, C., & Voisin, C. (2018): Patterns of Reservoir‐Triggered Seismicity in a Low‐Seismicity Region of France, Bulletin of the Seismological Society of America, 108(5B), 2967-2982.

How to use the application
After the User adds the application to his/her personal workspace, the following window appears on the screen (Figure 1):

Figure 1. Input window of Earthquake interactions (geo-resource scale) application.
This service analyses aftershock patterns around mainshock events within normalized distance to the trigger

Anchor
_GoBack _GoBack

shock targets (L^*= L_real/(L_f(M)).
For example: If mainshocks are selected as M2 events, L_f(M2) is close to 100 m, then the 1-3 L^* distances to select aftershocks will correspond to L_real= 1-3L_f(M2) (i.e. L^*= 1 x 100 = 100 m, and 3 x 100 = 300 m, respectively). Accordingly, the user, when using 1-3L^* distance to analyze near field triggering, will actually select earthquakes within 100-300 m range. Application inputs are M_m, and (ii) M_aft range for triggering and triggered shocks, respectively. To increase the signal-to-noise ratio, we use superposed epoch analysis. It corresponds to the restriction of each time series after a given event to a common t₀.
Outputs as aftershock rate over time may be compared to outputs of application "Earthquake interactions – geo-resource scale". We recommend torun the latter mentioned application with the same selection criteria on tectonic seismicity.
The user is now requested to fill in the fields shown below:
1) Use Seismic catalog: The user may click on "select files" button in order to use seismic catalog data among the ones that are already uploaded in his/her personal workspace.
2) Chosen Magnitude Column: The user may choose among different magnitude scales (e.g. M_L, M_W), in the Episodes where these scales are available.
3) Output file name prefix – File name for the output plot
4) Site name – Name of the site for which the episode is uploaded
5) Latitude range – Range of event latitudes used for reshuffling analysis
6) Longitude range – Range of event longitudes used for reshuffling analysis
7) Depth range – Range of event depths used for reshuffled analysis
8) Time range: Range of event times used for reshuffled analysis. Here, the user can select a time range by clicking boxes.
9) Location of geo-resource centre – The location of geo-resource zone centre
10) Geo-resource length – Length of the geo-resource zone
11) Relative distance – Relative distance to geo-resource zone: n x (geo-resource_length)
12) Mainshock magnitude range – Range of mainshock magnitudes used for superposed epoch analysis
13) Aftershock magnitude range – Range of aftershock magnitudes used for superposed epoch analysis
14) Bin size – Bin sizes for a given time period
15) Window duration – Number of days before/after the time that is used for superposed epoch analysis
16) Operated well location – Operated well location. This is optional. User may enter as many as possible wells (e.g. injection, extraction, waste water).
Figure 2 shows default values used for Lacq hydrocarbon field.

Figure 2. Default values for Lacq hydrocarbon field.

After defining the aforementioned parameters, the user shall click on the "Run" button and the calculations are performed. The Status changes from 'CREATED' to 'RUNNING' and finally to 'FINISHED'. The output is created and plotted in the main window just below the "RUN" button. The result appears in the left corner of the platform.
Figure 3 describes the outputs of Lacq field aftershock patterns.
It corresponds to seismicity rate in 6h window bins, 10 days before and after N=28 M3-3.7 events. Mean seismicity rate values before and after are shown as red and blue lines, respectively.




Figure 3. Triggering pattern (Lacq gas field). The selected mainshocks (trigger shock) are M3-3.7 events,. The selected triggered shocks (aftershocks) are Mé.2-3.3 events. Results are displayed as stacked time series (top figure), and cross section, (middle figures) and map bottom figure.