Haven't chased any newly occurred earthquake since I started my Global Supershear Earthquakes project. But this morning I had a fun chat with
and Bo about today's New Zealand earthquake and decided to run some high-resolution Back-Projection results. Looks interestin Image
One should pay extreme cautions if trying to interpret a "reverse rupture", as the resolution is marginal to resolve simultaneous sources with 10~30 km distance.
[Mar 7th] Major Update on the teleseismic back-projection result. Here is what seismic array I've analyzed. Numbers in parenthesis are number of stations for each array. I used vertical broadband (BHZ) and high-gain (HHZ) records. (1/n) Image
Here is the overview of the array analysis, in which I showcase the aligned waveforms, resolution kernels (array response), depth phase (pP) strength, and how all of these helped me determine data qualities of each array. (2/n) Image
Sub-event 1 (0-20 sec) is likely a thrust event dipping NEE with both along-strike and along-dip propagation.
The depth is approximately 60~90km, supported by both CMT solution and BP of depth phases (see sub-event 2). (3/n) Image
Sub-event 2 is likely a shallow (~20 km) normal fault dipping NWW. The dipping direction is inferred from the frequency-dependent characteristic: the cluster of higher-frequency radiations (left) locate NW to that of the relatively lower-frequency (right)... (4/n) Image
The eastward propagation is likely to be very robust and reliable, especially supported by the result of US array. This is because US array is located NW to the hypocenter, so the “non-toward-array” propagation is unlikely to be artifact of BP. (5/n)
Result of AU array migrate towards the AU array, which is likely caused by depth phases and swimming artifact, although it is not clear whether it is the depth phase of the sub-event 1 or sub-event 2. (6/n)
I'm thinking there is another sub-event occurred around 45 sec may be seen as early aftershock. Result of AU array most likely consist artifact, the swimming artifact that migrate toward the AU array. (7/n) Image
Not so sure if there is no rupture west to the hypocenter, although the result of AU is more likely to be artifact.
Spatial uncertainty of BP radiators can be as large as 20 km since slowness calibration that addresses travel time errors due to 3D path effect has ... (8/n)
has not yet been done. It is in my to-do list.
Depth phase related artifact is mostly addressed already, but coda wave related artifact may exist (e.g. velocity heterogeneity related scatters, or topography scatters)... (9/n)
Analysis will be done using empirical Green’s function (EGF) events.
Last but not least, big shoutout to @BaoningWu, @rokuwaki and @seismo_steve who helped me to organize random thoughts and inspired me. Much appreciated
Now it's time for sleep. 💤(end/n)

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