Enhancing post-seismic landslide susceptibility modeling in China through a time-variant approach: a spatio-temporal analysis

Figures & data

Figure 1. Jiuzhaigou M_S7.0 Earthquake. (a) The map shows the location of Jiuzhaigou, (b) Tectonic setting of the 2017 Jiuzhaigou M_S7.0 Earthquake (modified by Guo et al. 2021b). MJF: Minjiang Fault, NHYF: North Huya Fault, TZF: Tazang Fault.

Table 1. Remote sensing data used in this study.

Data type	Data sources	Data acquisition time	Spatial resolution (m)
Pre-seismic data	Google Earth images	2013/08/13 2015/10/21
	Sentinel-2 images	2017/07/29	10
Coseismic data	Image of emergency observation	2017/08/10	1
	Sentinel-2 images	2017/09/07	10
Post-seismic data	Sentinel-2 images	2019/09/27 2020/08/27	10
	Google Earth images	2019/09/27	0.5-1
	CW-15 UAV image	2020/06/10	0.16

Figure 3. Procedural flow chart of this study.

Figure 4. Example of 2017–2019 post-seismic landslides distribution buffer analysis.

Figure 5. Remote sensing images and field photo around Five Flower Lake. (a) 2013, (b) 2017, (c) 2020, (d) Field photo.

Figure 6. Remote sensing images and field photo around Mirror Lake. (a) 2013, (b) 2017, (c) 2020, (d) Field photo.

Figure 7. Remote sensing images and field photo around Heye community. (a) 2013, (b) 2017, (c) 2020, (d) Field photo.

Figure 8. Landslides area distribution after the 2017 Jiuzhaigou M_S7.0 earthquake. (a) 2017, (b) 2019, (c) 2020.

Figure 9. Post-seismic landslides. 2017–2019: (a) The Jiuzhaigou region, (b) The Jiuzhai Paradise region, (c) The Panda Lake region; 2019–2020: (d) The Jiuzhaigou region, (e) The Jiuzhai Paradise region, (f) The Panda Lake region.

Figure 10. Spatio-temporal distribution percentage of post-seismic landslides.

Figure 11. Examples of post-seismic landslides. Five-Flower Lake landslide edge: (a) 2017, (b) 2020; Heye landslide edge: (c) 2017, (d) 2020; Shuzheng landslide edge: (e) 2017, (f) 2020.

Table 2. Spatio-temporal distribution of post-seismic landslides in 2017–2019 and 2019–2020.

Buffer (m)	Post-seismic landslides within the buffer zone in 2017–2019		Post-seismic landslides within the buffer zone in 2019–2020
	Area (km^2)	Percentage of area (%)	Area (km^2)	Percentage of area (%)
50	2.59	71.49	3.15	93.17
100	2.88	79.59	3.25	96.27
150	3.01	83.15	3.28	96.90
200	3.09	85.30	3.29	97.32
250	3.14	86.74	3.30	97.65
300	3.18	87.88	3.31	98.06

Figure 13. Post-seismic landslide susceptibility calculated by the improved time-variant landslide susceptibility model. (a) 2017–2019, (b) 2019–2020.

Figure 14. Post-seismic landslide susceptibility calculated by conventional landslide susceptibility model. (a) 2017–2019, (b) 2019–2020.

Figure 15. Coseismic landslide susceptibility in 2017 (modified by Guo et al. 2021c).

Table 3. Changes of post-seismic landslide susceptibility distribution by the improved landslide susceptibility model.

Susceptibility	Percentage of classification area (%)
	2017	2017–2019	2019–2020
Very low	13.56	51.87	55.57
Low	22.65	23.83	24.71
Moderate	31.18	13.29	10.85
High	21.73	7.37	5.61
Very high	10.88	3.63	3.10

Table 4. Changes of post-seismic landslide susceptibility distribution by the conventional landslide susceptibility model.

Susceptibility	Percentage of classification area (%)
	2017	2017–2019	2019–2020
Very low	13.56	37.94	40.95
Low	22.65	25.87	26.51
Moderate	31.18	16.94	16.30
High	21.73	11.63	10.24
Very high	10.88	7.62	6.00

Table 5. 2019–2020 post-seismic landslides distributed in post-seismic landslide susceptibility classification area of 2017–2019.

Susceptibility	Percentage of classification area (%)
	Conventional model	Improved model
Very low	1.84%	2.52%
Low	5.00%	5.20%
Moderate	11.27%	12.21%
High	21.45%	24.15%
Very high	60.44%	55.92%

Table 6. Ranking of Pearson correlation coefficient in improved time-variant landslide susceptibility model.

Ranking	Pearson correlation coefficient
	2017		2017–2019		2019–2020
1	PGA	0.790	Fault	0.708	Distance	0.696
2	Fault	0.777	Distance	0.598	Fault	0.603
3	Strata	0.578	Slope	0.547	Slope	0.593
4	Slope	0.557	Aspect	0.407	PGA	0.428
5	Elevation	0.245	PGA	0.318	Aspect	0.396
6	Aspect	0.163	Strata	0.291	Strata	0.357
7	Road	0.142	Road	0.269	River	0.241
8	River	0.108	Elevation	0.152	Road	0.160
9			River	0.102	Elevation	0.026

Figure 16. Diagram showing the development of the new single post-seismic landslides. (a) Slope without landslide, (b) New single post-seismic landslides (u_w: Pore water pressure).

Figure 17. Diagram showing the development of the pre-phase landslides expansion. (a) Coseismic landslide, (b) Post-seismic landslide caused by cracks propagation, (c) Post-seismic landslide caused by deposits movements, (d) Post-seismic landslides caused by cracks propagation and deposits movements (u_w: Pore water pressure).

Guo, X. Y., B. H. Fu, J. Du, P. L. Shi, J. X. Li, Z. Li, J. X. Du, Q. Y. Chen, and H. Fu. 2021b. “Monitoring and Assessment for the Susceptibility of Landslide Changes After the 2017 Ms 7.0 Jiuzhaigou Earthquake Using the Remote Sensing Technology.” Frontiers in Earth Science 9: 633117. https://doi.org/10.3389/feart.2021.633117.

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Guo, X. Y., B. H. Fu, J. Du, P. L. Shi, Q. Y. Chen, and W. Y. Zhang. 2021c. “Applicability of Susceptibility Model for Rock and Loess Earthquake Landslides in the Eastern Tibetan Plateau.” Remote Sensing 13: 2546. https://doi.org/10.3390/rs13132546.

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Data availability statement

The data that support the findings of this study are available from the corresponding author, upon reasonable request.