Supplementary information of “Improving Back-Projection Imaging with a Novel
Physics-Based Aftershock Calibration Approach: A Case Study of the 2015 Gorkha
Earthquake”
Lingsen Meng1*, Ailin Zhang1 and Yuji Yagi2
1. Earth, Planetary and Space Sciences, University of California, Los Angeles, CA 90025, USA.
2. Dept. of Earth Evolution Sciences, Tennodai 1-1-1, Tsukuba 305-0006, Japan
*meng@ess.ucla.edu, 1805 Geology Building
University of California, Los Angeles, Phone: (310) 825-1885
Figure S1: The inset shows vertical component seismograms of the European (EU), Australian
(AU) and North American (NA) arrays filtered from 0.5 to 2 Hz, aligned on their first P arrival
and normalized by the standard deviation of their first 10 s.
Figure S2. Synthetic tests of kinematic rupture models. The colored squares in the left and right
columns shows the back-projection of a unilateral rupture of five uniform sources (stars) before
and after the slowness correction, respectively. The top, middle and bottom rows show the results
of the AU, NA and EU arrays. The squares are colored by time and sized by power.
Figure S3. The back-projections with a single-aftershock correction. Symbols denote backprojection radiations imaged by different arrays, (a) and (b) compare aftershock locations inferred
from back-projection with catalogue location before (a) and after (b) slowness correction. The
stars show NEIC catalogue locations of the M6.7 aftershock, with symbols (circle, square and
diamond) denoting apparent back-projection locations imaged by the AU, NA and EU array. (c)
and (d) show the mainshock back-projections of different arrays before and after correction. (e)
show rupture patterns of three arrays color-coded by time. Triangles with white edges are
comprehensive back-projection results combining all three arrays.
Magnitude
M5.5
Origin time
5/12/15 7:17
lat0
27.88
M6.7
4/16/15 7:09
27.78
M6.3
5/12/15 7:36
27.62
M5.7
4/25/15 6:18
27.55
Network
lon0
85.75 AU
NA
EU
86 AU
NA
EU
86.17 AU
NA
EU
86.08 AU
NA
EU
lat1
27.71
27.88
27.83
27.74
27.83
27.8
27.56
27.6
27.64
27.5
27.56
27.56
lon1
85.87
85.86
85.5
86.1
85.97
85.82
86.3
86.2
85.93
86.36
86.29
85.88
lat2
27.89
27.82
27.85
27.82
27.76
27.79
27.67
27.72
27.67
27.61
27.59
27.62
lon2
85.7
85.77
85.67
85.92
86.04
86.01
86.18
86.16
86.13
86.22
86.11
86.12
Table S1: Origin and location parameters of the calibration aftershocks. The latitude and
longitude numbered by 0, 1 and 2 denotes the epicenter location of the ISC catalog, the apparent
source location inferred from BP and source location inferred from BP with the slowness
calibrations.