# Ground-motion heterogeneity across four subdomains in Yunnan, China revealed by generalized spectral inversion

## TL;DR

The study reveals how ground motion varies in different regions of Yunnan, China, using earthquake data and inversion techniques.

## Contribution

The paper introduces a new method for analyzing ground-motion heterogeneity across tectonically distinct subregions in Yunnan.

## Key findings

- Stress drops in Regions C and D are higher than in Regions A and B.
- Reverse-faulting events show higher average stress drops compared to other fault types.
- Eastern regions (C and D) have lower Q0 and stronger S-wave attenuation.

## Abstract

This study investigates regional ground-motion characteristics in Yunnan Province using 1,065 recordings from 60 small-to-moderate earthquakes (3.0 ≤ Mw ≤ 6.0) at 65 stations. A generalized inversion technique (GIT) using empirical reference site was applied to four tectonically distinct subregions (A–D). The inversion results reveal stress drops (Δσ) ranging from 0.3 to 7.34 MPa, with the highest averages in Regions C and D (2.21 MPa), followed by Region A (2.07 MPa) and Region B (1.16 MPa). Δσ shows no clear dependence on moment magnitude (Mw) or focal depth but correlates with surface heat flow. Reverse-faulting events exhibit a higher average Δσ than strike-slip and normal-faulting events. Quality factor models for the four study areas (A–D) are 118.41f
0.691, 120.26f
0.638, 77.20f
0.598 and 72.19f
0.861, respectively. The eastern regions (C and D) exhibit lower Q0 and stronger S-wave attenuation, along with higher tectonic activity and lower surface heat flow. The predominant frequencies of average site amplification for GMX-A, GMX-B, GMX-C and GMX-D are 20.00 Hz, 10.83 Hz, 3.97 Hz, and 1.92 Hz, with corresponding amplification factors of 2.84, 4.31, 5.45, and 7.69. Finally, the inversion parameters were validated through stochastic finite-fault simulations of the 2009 MS 6.3 Yao’an mainshock.

The online version contains supplementary material available at 10.1038/s41598-025-24103-7.