Collaborative Research: Understanding the crustal link between the Columbia River flood basalts and lithospheric foundering.

合作研究：了解哥伦比亚河洪水玄武岩与岩石圈沉没之间的地壳联系。

• 批准号: 1546635
• 负责人: Robert Clayton
• 金额: $ 22.76万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2021-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1546635&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; crustal; link

The Earth?s largest volcanic events are the rare flood-basalt eruptions that occur once every about 40 million years, on average. Some of these events appear to have caused major extinctions, and in net, the erupted lavas cover a significant portion of the Earth; they also represent the beginning of hotspots such as Yellowstone. The most recent and best-exposed flood basalt event erupted about 16 million years ago from eastern Oregon. This is the target of our study. The fundamental driving mechanism for flood basalt eruptions occurs below the lithospheric plate, and the event has a major effect on modifying the plate. Yet, we do not understand the fundamentals of these events. It our case, there is strong evidence that large pieces of the affected lithosphere foundered and sank into the asthenosphere, and that the distribution of the foundering lithosphere controlled the location and distribution of volcanism. Our study will use seismic imaging methods to image the structures created and modified by this event, both in the crust and in the underlying lithosphere and asthenosphere, with the specific goals of finding the primary magma chamber(s) and resolving their shape.We will deploy about 60 seismometers in a line extending north 150 km from the center of the main eruptive center in northeast Oregon into southwest Washington, out of the eruptive area. We will use seismic waves that propagate up from distant earthquakes that occur around the world. The two primary techniques to be employed involve (1) the conversion of P waves to S waves that occurs when the wave hits an interface (such as the boundaries of the now-frozen magma chamber(s) we are studying), and (2) the time advance (or delay) that occurs for each ray as it passes through the region of interest. These delays are used to make a tomographic image of the major volumes of Earth that have been created by the flood basalt event.

地球？世界上最大的火山事件是罕见的洪水玄武岩喷发，平均每4000万年发生一次。这些事件中的一些似乎已经造成了重大的破坏，净而言之，喷发的熔岩覆盖了地球的很大一部分;它们也代表了黄石公园等热点的开始。最近和暴露最好的洪水玄武岩事件爆发约1600万年前从东部俄勒冈州。这是我们研究的目标。溢流玄武岩喷发的基本驱动机制发生在岩石圈板块之下，事件对板块的改造具有重要作用。然而，我们不了解这些事件的基本原理。在我们的例子中，有强有力的证据表明，大块受影响的岩石圈下沉并沉入软流圈，下沉岩石圈的分布控制了火山活动的位置和分布。我们的研究将使用地震成像方法来成像这次事件在地壳和下面的岩石圈和软流圈中产生和改变的结构，具体目标是找到原始岩浆房并解析其形状。我们将部署大约60个地震仪，从俄勒冈州东北部的主要喷发中心向北延伸150公里，进入华盛顿西南部，从火山爆发的区域。我们将使用地震波，它从发生在世界各地的遥远地震中传播出来。两种主要的技术包括：（1）P波到S波的转换，这发生在波撞击界面（例如我们正在研究的现在冻结的岩浆房的边界）时，以及（2）每条射线通过感兴趣区域时发生的时间提前（或延迟）。这些延迟被用来制作由洪水玄武岩事件产生的地球主要体积的断层图像。