Dear experts,
in the following figure has the information of focal mechanism with representative of the ball sphere, my question how is this can be created?
Really appreaciate any information that you can provide.
Dear Mel Varane,
There are several ways to plot focal mechanisms into beachballs. We can plot this data through the Obspy python library (see obspy.imaging.beachball).
In my opinion, a more straightforward approach is to use the ObspyDMT library by Kasra Hosseini. We can easily request event metadata:
obspyDMT --datapath neic_event_metadata --min_mag 5.5 --min_date 2014-01-01 --max_date 2015-01-01 --event_catalog NEIC_USGS --event_info
Furthermore, plot the beachballs:
obspyDMT --datapath neic_event_metadata --local --plot_ev --plot_focal
Best wishes!
Iago Sousa Lima Costa
Geophysicist at Geological Survey of Brazil (CPRM)
There are also approaches available through ESRI products. Such as:
https://pubs.usgs.gov/ds/2007/241/
https://www.arcgis.com/home/item.html?id=380b8f93cd684dbea56083218a3b2f43
Dear Mel Varane.
The ball scope of the earthquake foci mechanism can be created using the old ArcView program, the one that was the previous version of ArcGis.
Maybe there are other programs.
Mel,
The figure you mention consists of two data sets.
The first one is the background, with geographical and tectonic information. It will be a reference related to that background, i.e. a paper printed in a Geological journal, a Geological map and so on.
The second data set is represented by the beachballs.
For relatively moderate or major earthquakes, routinely with the magnitude Mw exceeding 5.0, the focal mechanisms are evaluated by Global Centroid Moment Tensor Project. You may download the beachballs into a certain area and time interval from their site.
Other institutions provide beachballs too, like GFZ Potsdam, ETH Zurich, IPGP France and so on. The beachballs are also summarised at International Seismological Center ISC. Enter on the corresponding sites and see in detail.
For small earthquakes, beachballs are evaluated by local or regional seismological agencies, routinely by using the polarities of the first arrivals. There are classic codes to do that, like the "focmec" code. You may find that code in the SEISAN package developed at Bergen and widely used.
Finally, you have to assemble the two data sets. You may do that with various codes, as indicated above. I would add also Generic Mapping Tool, widely used in Seismology or simply CorelDraw.
you can also use many ways to calculate the focal mechanism, such like HASH, using the ratio of the P and S amplitude with first arrival polarities. Or you could inverse the focal mechanism using synthetic full waveforms, many papers have provide these. For plotting, you could use obspy or GMT as well.
It can be plotted in GMT software by using psmeca command
You can follow this link too.
http://gmt.soest.hawaii.edu/doc/5.4.5/supplements/meca/psmeca.html
Thank you.
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