Seismic Surface Deformation Risks in Industrial Hubs: A Case Study from Ulsan, Korea, Using DInSAR Time Series Analysis

Abstract

The unprecedentedly strong 2016 Gyeongju and 2017 Pohang earthquakes on the Korean Peninsula aroused public concern regarding seismic hazards previously considered improbable. In this study, we investigated the effects of recent seismic activity close to the epicenters of both earthquakes in the heavy industrial complex of Ulsan. This was performed using Sentinel-1 InSAR time series data combined with on-site GPS observations and background GIS data. The interpretations revealed ongoing topographic deformation of a fault line and surrounding geological units of up to 15 mm/year. Postseismic migrations through the fault line, coupled with the two earthquakes, were not significant enough to pose an immediate threat to the industrial facilities or the residential area. However, according to InSAR time series analyses and geophysical modelling, strain from the independent migration trend of a fault line and eventual/temporal topographic changes caused by potential seismic friction could threaten precisely aligned industrial facilities, especially chemical pipelines. Therefore, we conducted probabilistic seismic hazard and stress change analyses over surrounding areas of industrial facilities employing modelled fault parameters based on InSAR observations. These demonstrate the potential of precise geodetic survey techniques for constant monitoring and risk assessment of heavy industrial complexes against seismic hazards by ongoing fault activities.

InSAR Time Series Analysis to Evaluate Subsidence Risk of Monumental Chandigarh City (India) and Surroundings

“…3(e) for decomposition. We have applied a least squares quadratic fit with a 2nd order polynomial form to synchronize ascending/descending observations in common timings together with a offset to adjust little temporal mismatch between selected ascending/descending time coverage as developed in Yun et al [55]. The referenced time frame is descending mode; thus, ascending mode data sets were interpolated.…”

“…This corresponds with the strong spatial heterogeneity of groundwater depletion, discharge of river sediments and geomorphological [62]. In particular, the test sites around Chandigarh city center are characterized by high variability in groundwater level due to the limited and highly heterogeneous distribution of aquifer sediment in the subsurface and with the population density consuming more water [54,55]. In Chandigarh, groundwater is being tapped from deep aquifers that are confined to nature.…”

Quaternary lava tubes distribution in Jeju Island and their potential deformation risks

“…conventional surveys to observe minor surface migration over a long period of time. Those have been successfully exploited for the detection of underground stability caused by depressurization, cavity creations and subtle surface creep (Baer et al, 2018;Intrieri et al, 2015;Hooper et al, 2004;Yun et al, 2019). Thus we expected the surface deformation on shallow lava tubes and cavities in Jeju Island are in the scope of InSAR observation accuracy estimated to a few millimetres.…”

The Survey of Lava Tube Distribution in Jeju Island by Multi-Source Data Fusion

“…The technology of space geodesy, such as InSAR data analysis, is widely used to observe minor surface migration over a long period. This has been successfully exploited to detect underground stability caused by depressurization, cavity creations, and subtle surface creep [45][46][47][48]. Thus, we expected the surface deformation on shallow lava tubes and cavities in Jeju Island are in the scope of InSAR observation accuracy estimated to be a few millimeters.…”