Figure 3 An example of the P-wave onset time picking by PickNet
(Wang et al., 2019) using vertical-component records of the 10 February
2019 MW5.0 event in the border region between Myanmar
and India (epicentre and station locations shown by the black dot and
triangles in Figure 1). The station name is given in the beginning of
each trace, and the red vertical line shows the picked P-wave onset
time. (a) 600-s long records
starting from the earthquake original time. (b) Zoom-in views of the
records in (a) in 20-s-long windows starting from 10 s before the
theoretical P-wave arrival times in AK135 model (Kennett et al., 1995).
All waveforms are self-normalized by the maximum amplitudes.
To evaluate the coverage of our dataset, we calculate the number of the
first-arriving P-wave ray paths through each 0.2° × 0.2° cell at
different depths, and the results are displayed in Figure 4. The ray
path density distribution shows that both the lower crust and uppermost
mantle (depth range 45-70 km) are generally well sampled by the dataset,
with large parts of the region having ray paths of more than 150 in each
cell. The density of the ray paths increases from the lower crust to the
uppermost mantle. With the decrease of the takeoff angles for longer
distances, sampling points at greater depths increase, particularly in
the uppermost mantle where the ray paths are nearly horizontal, as shown
in Figure 2. This implies that our dataset may provide better resolution
in the uppermost mantle than that in the lower crust.