InSAR Evidence Indicates a Link Between Fluid Injection for Salt Mining and the 2019 Changning (China) Earthquake Sequence

Abstract

In June 2019, an earthquake sequence comprising five M > 5 events occurred in a region of southwest China with fluid injection for both hydraulic fracturing and salt mining, which raised an extensive controversy on the cause. Here we use interferometric synthetic aperture radar (InSAR) observations to determine the source parameters of the sequence and to investigate the relationship with local injection activities. Both Sentinel‐1 and Advanced Land Observing Satellite 2 SAR images are collected to measure coseismic and preseismic surface deformation. Geodetic inversions with coseismic observations show that the sequence ruptured a previously unmapped southwest‐dipping thrust fault above 3 km depth, which intersects with the open‐hole sections of wells for solution mining of salt. In the 4 months before the sequence, cumulative line‐of‐sight displacements near the wells are around 1–2 cm after correcting seasonal‐like deformation. Our results indicate that water injection likely enhanced pore pressure within the fault zone and thus contributed to inducing the sequence.

Three Mw ≥ 4.7 Earthquakes Within the Changning (China) Shale Gas Field Ruptured Shallow Faults Intersecting With Hydraulic Fracturing Wells

“…Apart from recent HF‐related fluid injection, there is another kind of fluid injection at depths of 2.7–3.0 km for solution mining of salt (Figures 1a and 2a) that has been active for more than 30 years. These injection activities probably have caused dramatic increases in seismicity along the anticline, including a remarkable Mw 5.7 earthquake sequence in June 2019 (Lei et al., 2019b; S. Wang et al., 2020). With two different kinds of active fluid injection operations, it is important to characterize seismogenic faults in the region to better understand the causative mechanisms for injection‐induced seismicity.…”

“…To evaluate the quality of each interferogram, we first qualitatively check whether the interferograms with different temporal baselines or from different tracks show similar deformation patterns for each event. We then quantitatively check whether the interferograms of each event from the same track with different temporal baselines have comparable standard derivations, which are estimated based on the pixel values outside of major deformation regions (S. Wang et al., 2020). Lastly, to mitigate contamination from some unknown or unmodeled factors, only the interferograms passing through the first two rounds of screening with the shortest temporal baselines are chosen for each event.…”

“…Even with numerous moderate‐magnitude events across the globe now recognized as HF‐induced (Atkinson et al., 2020; Schultz et al., 2020), they are seldom detected and characterized with geodetic techniques. InSAR approaches have been widely used to investigate natural earthquakes as well as some events induced by anthropogenic injection/production activities and have been demonstrated with prominent abilities to image 3D geometries of seismogenic faults and high‐resolution rupture details (e.g., Grigoli et al., 2018; Jiang et al., 2018; S. Wang et al., 2020; Yi et al., 2017). Yet so far HF‐induced earthquakes were seldom investigated with InSAR: only Yang et al.…”

InSAR Modeling and Deformation Prediction for Salt Solution Mining Using a Novel CT-PIM Function

“…The multi-temporal interferometric synthetic aperture radar (MT-InSAR) is an advanced space-to-earth observation technology developed in recent years. Compared with traditional InSAR technology, MT-InSAR technology has been reported to be more effective and applicable for deriving ground deformations (i.e., mining area or infrastructures) [4][5][6][7][8][9][10][11][12][13]. However, the single MT-InSAR has a limitation in that it can only obtain the deformation sequences during SAR acquisition dates; the subsequent future displacement beyond the span of the SAR observations cannot be acquired.…”

Physics‐Based Evaluation of the Maximum Magnitude of Potential Earthquakes Induced by the Hutubi (China) Underground Gas Storage

“…This represents a potentially looming crisis since UGS operations can expose local communities to the potential risks of surface deformation and induced seismicity (Gaite et al., 2016; Priolo et al., 2015; Tang et al., 2018; Zhou et al., 2019; Jiang et al., 2020). Moreover, induced earthquakes in populated areas caused by other anthropogenic fluid injection and extraction activities appear to be growing in scale and frequency (e.g., Chen et al., 2017; Lee et al., 2019; Lei et al., 2019; McGarr et al., 2015; S. Wang et al., 2020). Recent attempts to control the size of induced earthquakes at two EGS sites have been successful (near Helsinki, Finland; Kwiatek et al., 2019) but also disastrous (Pohang, Korea; Kim et al., 2018).…”