Publication Date:
2024-05-23
Description:
Geofluids from natural springs connect with the crust and/or mantle in many cases, and their geochemical
anomalies could be significant for the study on faults activity and even earthquakes. Several natural springs are
distributed along the Lenglongling fault zone (LLLFZ) in the northeastern margin of the Tibetan Plateau, where
the Ms 6.9 Menyuan earthquake occurred on January 8th, 2022. Based on chemical and isotopic compositions
(δD, δ18O, δ13C, and 3He/4He) of water and gas samples, the origin of geofluids and their potential correlation
with fault activity even including earthquakes are preliminarily assessed in this paper. The δ13CCO2 values and
3He/4He ratios showed that the gas originating from the crust was associated with the metamorphism of carbonate
rocks, whereas the δ18O and δD values of water samples indicated that the natural springs were predominantly
infiltrated with precipitations from local mountains ranging 3.7 - 5.5 km in height. Obvious changes
of Ca2+ and HCO3 concentrations in SZK spring waters in the surface rupture zones were observed in a short
period (about three months) after the main shock, in contrast to those of the GSK springs far from the surface
rupture zones. Such variations might be correlated with the stress increase prior to the 2022 Menyuan Ms 6.9
earthquake. The mechanical fracturing of surrounding limestone rocks during the slipping movement of LLLF
could facilitate the water-rock interactions. Compared to three-month observations after the main shock, relatively
higher concentrations of HCO3 and heavier δ18OH2O values of the LHG springs were also observed in the
short-term period. The shallow stored formation water might be squeezed along the cracks and rose to the surface
during earthquake tremors, causing a sandblasting water phenomenon.
Description:
Published
Description:
105767
Description:
JCR Journal
Keywords:
Menyuan earthquake
;
Natural spring
;
Fluid geochemistry
;
Lenglongling fault
;
Tibetan plateau
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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