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Spatial variations of rockfalls from a growing lava dome: Soufriere Hills Volcano, Montserrat.

机译：不断增长的熔岩穹顶造成的落石的空间变化：蒙特塞拉特的Soufriere Hills火山。

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摘要

The lava dome at Soufriere Hills Volcano poses a physical hazard to nearby inhabitants. When the lava dome collapses, pyroclastic flows are generated that can travel several kilometers from their source. Understanding the behavior of lava domes is often performed using rockfalls produced by gravitational instabilities on the lava dome. Rockfalls generate seismic signals from which seismic energy can be extracted. Previous work has demonstrated that rockfalls may be locatable based upon their seismic energy, and this work develops a continuation of that approach. Rockfall direction and intensity is most likely determinable by seismic energy distribution as measured by the seismic station network, thus not requiring direct visual analysis, as clouds often cover the lava dome at Soufriere Hills Volcano. In this work, a technique was developed, which allows seismic data to be used to both identify and locate small rockfalls, a predecessor to most lava dome collapses.;Digital photographs of the lava dome from remote cameras and rockfall seismic energy data from 11 February 2006 - 1 May 2007 were utilized to visually confirm rockfall seismic event locations. From a set of 25, 297 seismic events, 1180 of these were visually confirmed and assigned a controlled location based in one of four quadrants surrounding the lava dome (i.e. quadrant one represented north, quadrant two represented east, etc.). From this dataset, a seismic energy-based mapping system was implemented; contours of equal energy were calculated using a cubic spline interpolation based on the total energy recorded for each seismic event. The energy mapping displayed each rockfall location in one of four quadrants, displaying results from both the cubic spline interpolation and the control dataset. Two different energy maps were created to compare the initial and final directions of rockfall runout.;Results of the seismic energy-based mapping yielded event initial rockfall location accuracies of 58%, 48%, 9% and 13% for quadrants one through four respectively. Final rockfall location accuracies were 61%, 41%, 10%, and 14% for quadrants one through four respectively. Ratios of seismic energy between seismic stations often produced two distinct trend lines of strong data scattering for seismic events located in quadrant one; both phenomenon were believed to be caused by path effects on seismic energy. Visually, the energy mapping was able to accurately indicate the direction of dome collapse prior to collapse events on 20 May 2006, 30 June 2006 and 8 January 2007. Actual rockfall runout direction was found to be controlled by current lava dome dimension. Rockfall frequencies prior to collapse were variable and not necessarily indicative of collapse immanency. Sources of inaccuracy were identified to be path effects on seismic energy distribution, and the availability and quality of seismic data. With improved accuracy, the method of seismic energy-based mapping of rockfalls could be a useful tool in real-time hazard mitigation, having already demonstrated an ability to forecast the direction of dangerous lava dome collapse material runout.
机译：Soufriere Hills Volcano的熔岩穹顶对附近居民造成了身体伤害。当熔岩穹顶坍塌时，就会产生火山碎屑流，这些火山碎屑流会从其源头传播几公里。通常通过使用熔岩穹顶上的重力不稳定性产生的落石来了解熔岩穹顶的行为。落石产生地震信号，可以从中提取地震能量。先前的工作表明，落石根据其地震能量可能是可定位的，并且这项工作发展了该方法的延续。落石的方向和强度最有可能由地震台站网络测得的地震能量分布来确定，因此不需要直接的视觉分析，因为云层通常覆盖了Soufriere Hills Volcano的熔岩穹顶。在这项工作中，开发了一种技术，该技术允许将地震数据用于识别和定位小熔岩崩塌（大多数熔岩穹顶坍塌的前身）.2月11日从远程摄像机获得的熔岩穹顶的数字照片和2月11日以来的崩塌地震能量数据2006年至2007年5月1日被用于视觉确认落石地震事件的位置。在一组25个，297个地震事件中，目视确认了其中1180个地震事件，并根据围绕熔岩穹顶的四个象限之一（即，象限一个代表北，象限两个代表东等）分配了受控位置。从该数据集中，实施了基于地震能量的制图系统；根据每次地震事件记录的总能量，使用三次样条插值法计算出等能量的等高线。能量映射在四个象限之一中显示每个落石位置，同时显示三次样条插值和控制数据集的结果。创建了两个不同的能量图以比较落石跳动的初始方向和最终方向;基于地震能量的映射结果得出，第一象限至第四象限的事件初始落石位置精度分别为58％，48％，9％和13％ 。一至四象限的最终落石位置准确度分别为61％，41％，10％和14％。地震台站之间的地震能量之比通常会针对位于第一个象限的地震事件产生两条截然不同的强数据散射趋势线。两种现象均被认为是路径对地震能量的影响所致。在视觉上，能量映射能够准确地指示2006年5月20日，2006年6月30日和2007年1月8日坍塌事件发生之前穹顶坍塌的方向。发现实际的落石跳动方向受当前熔岩穹顶尺寸的控制。倒塌之前的落石频率是可变的，并不一定表明倒塌的内在性。不准确的根源被确定为对地震能量分布，地震数据的可用性和质量的路径影响。随着精度的提高，基于地震能量的落石图绘制方法可能是实时减轻灾害风险的有用工具，并且已经展示了预测危险熔岩穹顶坍塌物质跳动方向的能力。

著录项

  • 作者

    Nimlos, Erik.;

  • 作者单位

    State University of New York at Buffalo.;

  • 授予单位 State University of New York at Buffalo.;
  • 学科 Geology.
  • 学位 M.S.
  • 年度 2009
  • 页码 81 p.
  • 总页数 81
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;
  • 关键词

  • 入库时间 2022-08-17 11:38:27

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