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Characterization of volcanic and land subsidence hazards at regional scales: Contributions from space geodesy.

机译：区域尺度上火山和地面沉降危害的特征：空间大地测量学的贡献。

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摘要

Remote sensing techniques have shown their capabilities in detecting ground deformation associated with a variety of natural hazards. However, most studies focus on relatively small areas, providing only spatially limited information, and many rely only on conventional Interferometric Synthetic Aperture Radar (InSAR), which lacks temporal resolution. The goal of this work is to perform systematic InSAR time series surveys at regional scales to improve volcanic and land subsidence hazards characterization in Indonesia and central Mexico.;An arc-wide InSAR time series survey along the west-Sunda arc, Indonesia, revealed unambiguous evidence that six dangerous explosive volcanoes inflated during 2007-2009, three of which erupted afterward (Chapter 2). A similar survey along the Trans-Mexican Volcanic Belt (TMVB), Mexico, did not reveal any volcanic inflation, reflecting a lower activity level (Chapter 3). Comparison between the two regions allowed characterization of the cases where InSAR can be used as a forecast tool for volcanic unrest. Closed volcanic systems present deformation cycles, as observed in the west-Sunda arc, eruptions being preceded by edifice inflation, while no significant ground deformation occurs prior to unrest at open volcanic systems (Chapter 3). The TMVB survey also revealed subsidence in the Paricutin lava field (Chapter 5). Detailed study highlighted that processes related to lava emplacement, even decades ago, especially due to cooling result in several centimeters per year of ground deformation. Such processes need to be considered to avoid misinterpretation of deformation fields in terms of changes in the magma plumbing systems at polygenetic volcanoes.;Magma reservoir depths were estimated using inverse modeling and regional trends in storage depths were revealed (Chapter 2). A global data compilation showed that these trends are explained by the crustal structure and stress regime of volcanic arcs (Chapter 4). Shallow magma reservoirs preferentially develop in young and thin crusts undergoing extensive or strike slip stresses, while the rates of melt generation in the mantle have no direct effect on crustal magma ascent. These observations have implications for volcanic hazard assessment and confirmed that large-scale surveys are useful to better understand general processes related to magma ascent.;Regional InSAR time series surveys were also applied to detect, map, and monitor land subsidence with high spatial and temporal resolutions in these two regions (Chapter 6 and 7). Results obtained show that land subsidence is a widespread problem and immediate actions are necessary to mitigate the risks associated with it. Combining the regional averaged velocity maps with other data sets such as land use, surface geology, and faults maps enabled identification of the parameters that influence the spatial distribution and the temporal evolution of land subsidence. Groundwater extraction appeared as the main cause of the rapid subsidence both in Indonesia and Mexico, confirming that subsidence is associated with a decrease in water access and quality.;In Indonesia nine subsiding areas were detected, including six major cities, the fastest subsidence occurring in densely populated coastal areas particularly vulnerable to flooding (Chapter 6). A continuation of the high subsidence rates will put these areas below relative sea level within a few decades. In central Mexico twenty-one subsiding areas including seventeen major cities were identified (Chapter 7). High velocity gradients exist in all the locations and often correlate with preexisting faults, motion on these faults being driven by water extraction. These high gradients present a threat to the integrity of buildings and infrastructures, some of these constructions being included in the UNESCO World Heritage list. The averaged velocity maps also revealed that faults act as barriers to groundwater flow, suggesting that they partition the aquifer systems at depths. Such observations have major implications for aquifer dynamics and need to be considered to achieve a more sustainable use of the groundwater resources at regional scales.
机译：遥感技术已经显示出它们检测与各种自然灾害相关的地面变形的能力。但是，大多数研究集中在相对较小的区域上，仅提供空间有限的信息，许多研究仅依赖于常规的干涉合成孔径雷达（InSAR），后者缺乏时间分辨率。这项工作的目标是在区域范围内进行系统的InSAR时间序列调查，以改善印度尼西亚和墨西哥中部的火山和地面沉降危害特征。沿印度尼西亚西桑达弧线进行的弧线InSAR时间序列调查显示明确有证据表明，在2007年至2009年期间，六座危险的爆炸性火山膨胀，其中三座随后爆炸（第二章）。墨西哥跨墨西哥火山带（TMVB）的类似调查未显示任何火山通货膨胀，反映出较低的活动水平（第3章）。两个区域之间的比较可以表征InSAR可以用作火山爆发预测工具的情况。封闭的火山系统呈现出变形循环，如在西桑达弧线中所观察到的那样，喷发之前是建筑物的膨胀，而在开放的火山系统发生动荡之前，没有发生明显的地面变形（第3章）。 TMVB调查还揭示了Paricutin熔岩田的沉降（第5章）。详尽的研究强调，甚至数十年前，与熔岩安置有关的过程，特别是由于冷却导致每年地面变形几厘米。需要考虑这样的过程，以避免对多基因火山岩浆管道系统中的变化造成的变形场的误解。岩浆储层深度是通过反演模型估算的，并揭示了储层深度的区域趋势（第二章）。全球数据汇编显示，这些趋势可以通过火山弧的地壳结构和应力状态来解释（第4章）。浅层岩浆储集层优先发育于经历了广泛应力或走滑应力的年轻和薄壳中，而地幔中熔体的生成速率对地壳岩浆上升没有直接影响。这些观测结果对火山灾害评估具有影响，并证实大规模调查有助于更好地了解与岩浆上升有关的一般过程。区域InSAR时间序列调查还用于检测，测绘和监测具有高时空分布的地面沉降这两个区域的分辨率（第6章和第7章）。获得的结果表明，地面沉降是一个普遍存在的问题，必须采取立即行动以减轻与地面沉降有关的风险。将区域平均速度图与其他数据集（例如土地利用，地表地质和断层图）结合起来，可以识别影响地面沉降的空间分布和时间演变的参数。在印度尼西亚和墨西哥，地下水开采是迅速沉降的主要原因，这证实了沉降与水的获取和水质下降有关。在印度尼西亚，共发现了9个沉降区域，包括6个主要城市，沉降速度最快。人口稠密的沿海地区特别容易遭受洪水侵袭（第6章）。高沉降率的持续发展将在几十年内使这些地区低于相对海平面。在墨西哥中部，确定了包括十七个主要城市在内的二十一个沉降区域（第7章）。高速梯度存在于所有位置，并且通常与先前存在的断层相关，这些断层上的运动是由抽水驱动的。这些高坡度对建筑物和基础设施的完整性构成了威胁，其中一些建筑物被联合国教科文组织列为世界遗产。平均速度图还显示断层是地下水流动的障碍，表明它们在深处划分了含水层系统。这种观测对含水层动力学有重大影响，需要加以考虑，以便在区域范围内更可持续地利用地下水资源。

著录项

  • 作者

    Chaussard, Estelle.;

  • 作者单位

    University of Miami.;

  • 授予单位 University of Miami.;
  • 学科 Geophysics.;Geology.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 294 p.
  • 总页数 294
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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