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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The anatomy of a lahar: Deciphering the 15th September 2012 lahar at Volcan de Colima, Mexico
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The anatomy of a lahar: Deciphering the 15th September 2012 lahar at Volcan de Colima, Mexico

机译：Lahar的解剖：2012年9月15日在墨西哥Volcan de Colima解密lahar

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Volcan de Colima is one of the most active volcanoes in Mexico where lahars are a common phenomenon. Since the reactivation of the volcanic activity in 1991, lahars have become more frequent during the June-October rainy season, in this region. Therefore, Volcan de Colima represents a natural laboratory, ideal for the constant monitoring of lahars and to study factors controlling their origin, flow transport and deposition. Since 2007 the systematic detection of lahars in Volcan de Colima has been carried out using seismic data from the broadband stations of the RESCO network, the seismological network of Colima University, along with three rain gauge stations located on the southern ravines of the volcano. In 2011 a new monitoring station was built at 2000 m.a.s.l. along the Montegrande ravine, which consists of a geophone, a video camera and a rain gauge station coupled with a moisture sensor, transmitting in real time to the RESCO facilities at Colima University. With all the instrumentation currently installed on the volcano flanks, we could monitor and describe the lahar that occurred on 15th September 2012 along the Montegrande ravine, and correlate the monitoring data with information gathered by the field campaign conducted two days after the event The high quality of collected data enabled us to describe the "anatomy" of this lahar. The event consisted of a lahar that lasted 40 min, triggered by 20 mm of accumulated rainfall with a maximum intensity of 95 mm/h. The lahar was characterized by three main surges at 4-5 minute intervals that formed an 80 cm-thick terrace. The first surge was a debris flow with a block-rich front followed by the main body that progressively diluted to a hyperconcentrated flow, from which a 40 cm-thick massive unit was emplaced (33 wt.% gravel and ＞60 wt% of sand); it was followed by a more dilute hyperconcentrated flow that left a massive 10 cm-thick sandy layer (80 wt.% of sand); the third surge deposited a 30-cm thick upper massive unit texturally similar to the first Laminated layers separate the two first units. Subsequent surges were confined to the inner portion of the channel by the newly formed terrace. Based on flow depth estimation and difference in arrival times between geophones, a mean velocity of 3 m/s and a maximum peak discharge of 48 m~3/s were estimated. Segregation processes that promote the upwelling of the largest clasts (20-30 cm) on the flow surface were also observed, resulting in a clast-rich levee on top of the de-positional units. A sedimentation rate of ～5-7 cm/min was also determined. The results here obtained are useful to better understand textural features of lahar deposits from which important information on flow behavior can be interpreted.
机译：火山科利马火山是墨西哥最活跃的火山之一，拉哈斯是普遍现象。自1991年恢复火山活动以来，在该地区的六月至十月雨季，拉哈尔变得更加频繁。因此，Volcan de Colima代表了一个天然实验室，是不断监测海豚的理想场所，是研究控制其起源，水流输送和沉积的因素的理想选择。自2007年以来，已利用来自RESCO网络，科利马大学地震学网络的宽带站以及位于火山南峡谷的三个雨量计站的地震数据，对科利马火山进行了系统的探测。 2011年，在2000 m.a.s.l.建立了一个新的监测站。沿着蒙特格兰德峡谷，由检波器，摄像机和带湿度传感器的雨量计站组成，实时传输到科利马大学的RESCO设施。借助当前安装在火山侧面的所有仪器，我们可以监测和描述2012年9月15日发生在蒙特格兰德河谷的拉哈尔河，并将监测数据与事件两天后进行的野战活动收集的信息相关联。收集到的数据使我们能够描述这种拉哈尔的“解剖”。该事件由持续40分钟的拉哈尔组成，由20毫米的累积降雨触发，最大强度为95毫米/小时。拉哈尔河的特征是，以4-5分钟为间隔的三个主要浪涌形成了一个80厘米厚的阶地。第一次涌浪是泥石流，其前部富含块体，随后是主体，逐渐稀释成高浓度流，从中移入了一个40厘米厚的块状单元（砾石含量为33％（重量），砂子含量> 60％（％） ）;随后是更稀的超浓缩流，留下了10厘米厚的巨大沙层（80％的沙子）；第三次浪涌沉积了一个30厘米厚的上部块状单元，其质地类似于第一层，将两个第一单元分开。随后的涌动被新形成的阶地限制在通道的内部。基于流量深度估计和检波器之间到达时间的差异，估计平均速度为3 m / s，最大峰值排放为48 m〜3 / s。还观察到促进流动表面上最大碎屑（20-30 cm）上升的分离过程，从而在沉积单元顶部形成了富含碎屑的堤坝。还确定了〜5-7 cm / min的沉降速率。此处获得的结果有助于更好地了解拉哈尔沉积物的质地特征，从中可以解释有关流动行为的重要信息。

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