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CelsoReyes / zmap7

ZMAP Seismology Software. V 7.x has been updated to MATLAB R2018a.
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Add ability to remove quarry blasts #11

Open CelsoReyes opened 6 years ago

CelsoReyes commented 6 years ago

Add ability to remove quarry blasts from catalog. Currently, ZMAP only takes the preliminary steps in the analysis.

References: Wiemer, S. and Baer, M., 2000. Mapping and removing quarry blast events from seismicity catalogs. Bulletin of the Seismological Society of America, 90(2), pp.525-530

Gulia, L., 2010. Detection of quarry and mine blast contamination in European regional catalogues. Natural hazards, 53(2), pp.229-249.

CelsoReyes commented 6 years ago

Notes on implementing this, lightly modified from personal comm. from Gulia:

2 options to possibly add.

1. Wiemer and Baer (BSSA,2000):

  1. Compute a map of Rq for 8 different N, ranging from N=4 50 to N=400.
  2. Translate each Rq(x,y,N) value into a probability of occurrence PRq(x,y,N)
  3. Find the most significant PRq(x,y,N) node. If this value exceeds the 99% confidence level, and the events are not mostly aftershocks, remove all daytime events for that particular node from the seismicity catalog.
  4. Iterate steps 1–3 using the modified data set until no node with PRq(x,y,N)>= 99% can be found. To eliminate aftershock sequences in step 3 we require that no more than 20% the daytime events occur on one day.

According to Wiemer and Baer (2000), an indicative value for the D/N ratio is 1.5.

2. Gulia (Gulia, NH, 2010): Proposing a preliminary analysis to be applied before the Wiemer and Baer procedure, to reduce the removal of real earthquakes.

  1. plotting the number of events per hour-of-the-day histograms for different M intervals (0.2 for a detailed analysis, 0.5 for a quicker one, from M=1 to M=4 or 5- like the ones in Figure 2 of my paper), to identify the maximum magnitude of the blasts;
  2. removing the aftershocks declustering the catalog;
  3. cutting the declustered catalog at the maximum M identified at the step 1;
  4. running the Wiemer and Baer standard procedure.

Some blasts in regions with aftershocks can still remain in the catalog, but we are pretty sure that no real earthquakes have been removed.

GeoBasem commented 5 years ago

Hi Dr.Celso Thank you very much for your great contributions. This implementation is very helpful and clear to me. I am currently trying to apply the same procedure using Zmap 6. but, unfortunately it's only the first step of Wiemer and Baer (BSSA,2000) procedure that is available, does Zmap 7. include the remaining steps?

Kind regards Basem