2023 Dec 04, 18:26:58
This was well recorded on 4 nearby Shakes
R9AF3 (30km from the Geosciences Australia epicentre)
R811A (52km)
R571C (112km)
R6D2A (126km)
with the arrival times of the closest pair being quite discrepant from the Geosciences Australia (GA) hypocentre (some seconds). GA don’t seem to ever use Shake data and the closest stations used in their analysis are
AUDCS (92km)
AUPHS (167km)
MGCD (178km)
It would be nice if someone could do an analysis using the Shake data.
I think you can see the timing issue with the close stations in the section plots.
My first reaction to that was “Hmm that’s not a good fit”, but I need to remind myself that seismology is not necessarily a precise science. The arrival times are based on models which use average figures for wave speeds for all types of rock. The closer a station is, the less likely that signal will pass through all types of rock to achieve the right average speed. So it may just bee that the rock between Ulan and Mudgee is “fast”.
The other factor may be that earthquakes may be quite spread over an area on a fault, so very close stations may start to see the signal from the closest part of the quake area significantly earlier than the centre of the quake area.
I have been doing quite a few section plots on mine blasts recently, and as mine blasts (in NSW) are always <1km deep and quite small in area it often allows me to identify the source mine, but there are times when the fit just isn’t good enough and I have to settle for the area. I put this down to the speed variations through the rock.
Al.
At the risk of repeating myself, this is a great analysis job sheeny!
Glad to see the local section plots have come out as they appear! Lots of information packed in a single output.
Thats a brilliant job, and great to see my RS used in the analysis too.
A warm welcome to our community then LithgowLights! Happy to have you with us!
