Geodetic/gravimetric evidence for mass loss in the subsidence area of Bandung, Indonesia

IF 2.1 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Brian Bramanto , Kristian Breili , Christian Gerlach , Irwan Gumilar , Vegard Ophaug , Eko Januari Wahyudi
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Abstract

Land subsidence monitoring in Bandung, Indonesia, was initiated in the 2000 s. However, the monitoring has been limited to geometric observations only, which may restrict the further physical interpretation of the cause of the subsidence. In this study, we combine geometric and gravity observation methods to monitor surface subsidence in Bandung. 63 Synthetic Aperture Radar (SAR) images from Sentinel-1A covering the period of 2014–2020 were used to estimate the mean surface geometric changes. For the gravity observations, a hybrid gravity configuration that incorporates absolute (2008–2014) and relative (2011–2016) gravity observations were used to estimate the gravity changes. We estimated geometric changes of up to − 160 mm/yr, indicating rapid subsidence in the greater Bandung area. We obtained gravity changes ranging between − 56.7 and 40.1 μGal/yr. Upon subtracting the deformation-induced gravity field from the observed field, we produced a residual gravity field that was presumed to be dominated by the groundwater signal, which was then investigated further. We found that the gravity-derived groundwater signal was mainly negative, indicating subsurface mass loss. We further compared the signal with the modeled gravity effect from deep groundwater observations (1996–2008). The median difference between the observed and modeled groundwater gravity signal was estimated to be 2.8 ± 18.0 μGal/yr or equivalent to 0.08 ± 0.55 m/yr in terms of water height if we set the integration cap and groundwater depth to 1.4 km and 150 m, respectively. The discrepancy can be attributed to modeling (simple geohydrological assumption) and measurement (different observation periods and noise) factors. Nevertheless, both measurements indicate that the mass is decreasing due to groundwater depletion, demonstrating the potential of geometric-gravimetric observations to infer sub-surface mass loss.

印度尼西亚万隆沉降区质量损失的大地测量/重力证据
印尼万隆的地面沉降监测始于2000年代。然而,监测仅限于几何观测,这可能会限制对沉降原因的进一步物理解释。在本研究中,我们结合几何和重力观测方法来监测万隆的地表沉降。使用Sentinel-1A在2014-2020年期间的63张合成孔径雷达(SAR)图像来估计平均表面几何变化。对于重力观测,使用了包含绝对(2008-2014)和相对(2011-2016)重力观测的混合重力配置来估计重力变化。我们估计几何变化高达−160毫米/年,表明大万隆地区的快速沉降。我们获得了−56.7和40.1μGal/yr之间的重力变化。在从观测场中减去变形引起的重力场后,我们产生了一个残余重力场,该残余重力场被认为是由地下水信号主导的,然后对其进行了进一步的研究。我们发现重力引起的地下水信号主要是负的,表明地下质量损失。我们进一步将该信号与来自深层地下水观测(1996-2008)的模拟重力效应进行了比较。如果我们将积分上限和地下水深度分别设置为1.4 km和150 m,则观测到的地下水重力信号和模拟地下水重力信号之间的中值差估计为2.8±18.0μGal/yr,或相当于0.08±0.55 m/yr。这种差异可归因于建模(简单的水文地质假设)和测量(不同的观测周期和噪声)因素。然而,两次测量都表明,由于地下水枯竭,质量正在减少,这表明几何重力观测有可能推断地表下质量损失。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Geodynamics
Journal of Geodynamics 地学-地球化学与地球物理
CiteScore
4.60
自引率
0.00%
发文量
21
审稿时长
6-12 weeks
期刊介绍: The Journal of Geodynamics is an international and interdisciplinary forum for the publication of results and discussions of solid earth research in geodetic, geophysical, geological and geochemical geodynamics, with special emphasis on the large scale processes involved.
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