I am using ObsPy to download event information for many different events from USGS would like to get the centroid location and depth apart from the moment tensor. However, I am unsure which origin is associated with which focal mechanism.
The Kaikoura earthquake as an example:
import obspy from obspy.clients.fdsn import Client client = Client('USGS') t=obspy.UTCDateTime('2016-11-13T11:03:00') cat=client.get_events(starttime=t-60, endtime=t+60, minmagnitude=5, includeallorigins=True)
This finds an event with three origins and three focal mechanisms:
len(cat.origins) 3 len(cat.focal_mechanisms) 3
The third origin is marked as “from moment tensor inversion”:
cat.origins.depth_type 'from moment tensor inversion'
while this entry is empty for the other origins. However, the moment tensor is stored in the first focal mechanism entry:
cat.focal_mechanisms.moment_tensor.tensor Tensor m_rr: 4.81e+20 m_tt: 1.726e+20 m_pp: -6.537e+20 m_rt: -9.06e+19 m_rp: 2.986e+20 m_tp: -2.323e+20
The other focal mechanism entries do not contain a moment tensor.
How can I make sure to find the latitude, longitude and depth derived from the moment tensor inversion and the according focal mechanism even though both indices don’t coincide? If more than one moment tensor solution is present in the catalog, which one is the preferred / most reliable one?
Thank you very much for clarifying this issue!