Mon Oct 13, F. Flechtner
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Colledge, Martin, Chanard, Kristel, Duverger, Clara, Schubnel, Alexandre, Adhikari, Lok Bijaya, and Bollinger, Laurent, 2025. Annual variations in Nepalese seismicity: b-values and seismicity rates. Geophysical Journal International, 242(3):ggaf259, doi:10.1093/gji/ggaf259.
• from the NASA Astrophysics Data System • by the DOI System •
@ARTICLE{2025GeoJI.242..259C,
author = {{Colledge}, Martin and {Chanard}, Kristel and {Duverger}, Clara and {Schubnel}, Alexandre and {Adhikari}, Lok Bijaya and {Bollinger}, Laurent},
title = "{Annual variations in Nepalese seismicity: b-values and seismicity rates}",
journal = {Geophysical Journal International},
keywords = {Transient deformation, Asia, Statistical seismology, Fractures, faults, and high strain deformation zones},
year = 2025,
month = sep,
volume = {242},
number = {3},
eid = {ggaf259},
pages = {ggaf259},
abstract = "{Seasonal variations in Nepalese seismicity have been reported with
varying degrees of confidence. We re-investigate these claims by
analysing 20 yr of Nepalese seismicity before the 2015 Gorkha
earthquake, as detected by the Nepalese national network, and
focusing on earthquakes located along the eastern and central
sections of the Nepalese Main Himalayan Thrust. Using several
declustering techniques, we find no statistically robust
evidence of seasonal seismicity in the studied record,
regardless of magnitude threshold above completeness. This
suggests that previously reported seasonality may be restricted
to the western section of the Nepalese orogeny, may be an
artefact, or may indicate that nucleation times of earthquakes
are longer than the year. We also investigate potential annual
variations in the Gutenberg{\textendash}Richter b-value, given
its recent observed modulation by transient stressing.
Additionally, we use large-scale mass redistribution estimated
from the monthly gravity field retrieved from the Gravity
Recovery And Climate Experiment and Follow-On (GRACE/-FO)
missions, to resolve stress variations at depth induced by
transient surface loads. We find that the mean annual b-value
peaks when seasonal Coulomb stress rates reach their minimum
value at the height of the summer rainy season. When considering
the combined effect of tectonic and seasonal loading, this
corresponds to a recurring period of stress reversal, when
Coulomb stress momentarily decreases. This suggests that
periodic clamping of the Main Himalayan Thrust reduces the
likelihood of earthquakes growing to larger magnitudes in
accordance with hierarchical rupture models. The susceptibility
of b-value to stress variations of roughly 0.1 points.kPa is
consistent with recent estimates of b-value sensitivity to
transient loading, although it remains high when compared to the
stress-dependence associated with both static differential
stress, and with long-term evolution during the seismic cycle.
This discrepancy points to the large impact of stress transients
on the dynamics of seismic rupture.}",
doi = {10.1093/gji/ggaf259},
adsurl = {https://ui.adsabs.harvard.edu/abs/2025GeoJI.242..259C},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
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