Conference Agenda

In the framework of the ESA-MOST Dragon-6 project (id.95348), the Istituto Nazionale di Geofisica e Vulcanologia (INGV) from Italy, the Northeastern University (NEU), the Jilin Earthquake Agency and Jilin University from China are carrying out collaborative research using time-series radar and optical images on different geohazards in Northeast China.

Stemming from the experience of the previous Dragon-4 and Dragon-5 projects, the joint research team from Italy and China collaborated to monitor the deformation due to industrial activities and volcanic dynamics. In particular, we are continuing to measure and analyze the ground motion at the Fushun open pit mine and Changbaishan Tianchi volcanic complex to support local hazard assessment. In addition, we analyze the ground deformation at a new study site, the Songliao Basin. Songliao is a Mesozoic-Cenozoic continental basin characterized by significant oil and gas extraction activities and water exploitation. To investigate the surface motion affecting the basin, we mainly use InSAR data from Sentinel-1. The Songliao Basin appears to be affected by ground motion (subsidence and uplift) caused by natural phenomena and anthropogenic activities.

Our main goal is to identify and characterize the processes responsible for the deformation (fluid migration, slope mass movement, volcano dynamics, and human activities), hence quantifying the deformation caused by each source. To this aim, we model the degassing and magmatic activity at Changbaishan Tianchi by using the detected surface deformation and explore the correlation between deformation and the amount of oil/gas extraction or fluid pumping in deep wells in the Songliao Basin.

In detail, the Changbaishan Tianchi intraplate volcano is one of the most active and hazardous volcanoes of Northeast Asia, characterized by a summit caldera formed after the 946 CE ‘Millennium’ Plinian eruption. From December 2020 to June 2021, the frequency and magnitude of earthquakes were significantly higher than during background periods with hundreds of earthquakes (46 events per month on average) reaching a local maximum magnitude of ML 3.1. Our study reports a comprehensive deformation analysis and a geophysical inversion scheme aimed at unveiling the volcano dynamics in this period. Multi-temporal InSAR analysis results of 32 ALOS-2 images from 2018 to 2022 show that the surface deformation is a combination of seasonal fluctuations (± 25 mm in average, with a maximum ± 45 mm) and a long-term positive component. The least squares linear regression of the deformation time series and temperature data isolates the seasonal fluctuations, revealing a clear uplift and subsidence process from June 2020 to July 2021 in the caldera area. To constrain the Tianchi plumbing system dynamics, a combined inversion scheme consisting of three deformation sources is proposed. The inversion results and the seismic records indicate that the Tianchi volcano experienced a low-level unrest episode from December 2020 to June 2021. The shallower plumbing system, located at about 5–9 km depth and modeled by pressurized spheroids, underwent a cumulative volume increase of 26 × 10⁶ m³ from November 2018 to April 2021, followed by a volume decrease of 9 × 10⁶ m³ from April to July 2021. This suggests magma rising from a 14 km deep storage zone to the shallower plumbing system, followed by depressurization due to the escape of fluids. In the next years of the project, we will continue to monitor the Tianchi volcano complex using InSAR techniques and also considering images acquired by the ALOS-2 sensor operating in the L-Band, thus allowing a larger spatial coverage due to a lower sensitivity to vegetation.

Aiming at testing new monitoring procedures based on SAR and optical satellite data, the NEU and INGV teams have also investigated the Hunga Tonga-Hunga Ha’apai (HTHH) submarine volcano, providing an exhaustive analysis able to interpret the disastrous eruptive event that destroyed the island in January 2021. HTHH in the Tonga-Kermadec island arc initiated a new eruptive phase lasting approximately 1 month after 7 years of dormancy. This eruptive phase culminated in the January 15, 2022, Plinian eruption and the associated destructive tsunami. To analyze the complete eruption sequence from 2021 to 2022, satellite optical images and synthetic aperture radar images were analyzed, revealing the morphological changes of the volcanic island(s) during the time. The preparatory phase preceding the first eruption on December 19, 2021, was studied by considering descending Sentinel-1A images from 2020 to 2021. The obtained surface deformation before the December 2021 eruption shows an uplift of nearly 6.4 cm on the line of sight. Results reveal that a possible intrusion of magma started in May 2020 and gradually increased until December 2021, leading to a 19-month-long deformation phase before the eruption. The observed deformation is possibly explained by (a) a NNW-SSE striking, magma-filled dike upraising since the beginning of 2020 from a spheroid-like source located at 5000 m depth.

As far as the Songliao basin is concerned, we have analyzed Sentinel 1-A/B images belonging to different tracks to obtain the largest possible spatial coverage for such an area. To achieve this goal, we have selected SAR data along the descending orbit in the temporal interval between 2021-2024 for Sentinel-1A data for the northern part and Sentinel-1B data for 2017-2021. The latter was because the southern part of the basin was only covered by Sentinel-1B data, which was unfortunately discontinued in 2022. We processed more than 600 SAR images using the Small Baseline Subset technique and obtained the mean ground velocity and the displacement time series. Some very interesting phenomena were detected from these products, highlighting different behaviors, like subsidence and uplifting, for contiguous areas. In the Daqing area, where one of the larger oil fields of the Songliao basin is located, we have detected an uplift in the oil extraction area and a subsidence in the neighboring water network. Data show that for every ton of crude oil produced in the oil field area, 2-3 tons of water collected from the neighboring areas (the water basins and the city) need to be re-injected, and there are 36,879 m³/yr of oil-polluted wastewater. The detected ground deformation shows a subsidence in the water network area and uplift due to water injection in the oil field.

The resilience of vulnerable communities and agricultural systems against natural hazards—particularly landslides and land subsidence—needs to be strengthened. These events cause numerous fatalities and significant economic losses each year. Landslides primarily affect linear infrastructure and urban areas in mountainous regions, resulting in serious communication disruptions and loss of life. Meanwhile, land subsidence is emerging as an increasingly severe geohazard, expected to impact millions of people globally in the coming years by raising flood risks in urbanized areas and damaging critical infrastructure. In this contribution, we present the results obtained after one year of the ReSeLMAIN project (ID: 95355 – Remote Sensing for Landslide Monitoring and Impact Assessment on Infrastructure), developed within the framework of the Dragon-6 cooperation program—an initiative between the European Space Agency (ESA) and the Chinese Ministry of Science and Technology (MOST). The ReSeLMAIN project aims to employ remote sensing techniques, particularly Synthetic Aperture Radar Interferometry (InSAR), to identify, map, and monitor landslides and land subsidence, as well as assess their impacts on infrastructure.

We are working in various study areas across China and Spain. In Beijing, the capital of China, high-resolution TerraSAR-X data was used to analyze land subsidence induced by groundwater withdrawal, revealing a maximum mean displacement rate of over 110 mm/year between 2010 and 2019. A methodology based on slope gradient, vertical radius of curvature, and angular distortion calculated from InSAR-derived displacements has been developed to assess potential damage along the Beijing–Tianjin high-speed railway. In the eastern Tibetan Plateau, China, multi-platform SAR images from 2007 to 2022 were used to identify and characterize landslide groups, which pose grave peril to community members and critical construction along the Jinsha River. A novel InSAR-based method was developed to infer the slip surface of active landslides, along which the maximum displacement reached 1.5 m. We also found that in our study area, the 2018 Baige landslide failure had caused persistent acceleration to downstream wading landslides, highlighting the prolonged cascading impact of landslides on the watershed’s geological environment. In Monóvar, Spain, an Active Deformation Area (ADA) was identified using data from the European Ground Motion Service (EGMS). This area shows maximum vertical and east–west displacement rates of 64.6 mm/year and 23.8 mm/year, respectively, during the period from 2019 to 2024, affecting more than 6 hectares of partially urbanized land. While the deformation was initially attributed to a landslide, subsequent investigations have linked it to a subsurface dissolution process. Supporting evidence includes the concentration of structural damage in buildings located over gypsiferous substrata, the concentric pattern of surface cracking, and the identification of a characteristic subsidence bowl. The findings indicate that a significant number of buildings, roads, and other infrastructure in Monóvar are affected by these ground deformations, underscoring the need for improved monitoring and mitigation strategies.