Collaborative Research: Dynamics of the Southern Rocky Mountains from Cross-term Estimates of the Seismic Green Tensor

合作研究：根据地震绿色张量的跨期估计来了解落基山脉南部的动力学

• 批准号: 1142008
• 负责人: Vera Schulte-Pelkum
• 金额: $ 6.42万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-03-15 至 2016-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1142008&HistoricalAwards=false
• 关键词: Collaborative; Research; Dynamics; Southern; Rocky

This project centers on two questions: 1. What props up the Rocky Mountains of Colorado and New Mexico ? is the surface elevation high because of extra-thick, buoyant crust underneath, or is the crust no thicker than in the surrounding areas and it is instead hotter than usual mantle sitting underneath that supports the unusually high elevations? To answer this question, we must map the crust-mantle boundary under the Rockies. Conventional methods to do this have so far left a fair amount of ambiguity regarding crustal thickness. We propose to solve this by investigating question 2: Can we use a recently developed method that has been successfully applied to shallow geophysical problems, such as hydrological imaging, to find the much deeper crust-mantle boundary?We will use already collected seismic data sets and apply new analysis techniques to provide constraints on the dynamics of a tectonically enigmatic area. The Southern Rocky Mountain region has recorded a complex history of continental assembly, mountain building far from plate boundaries, and incipient continental rifting. Because the mechanism and timing of uplift of this large area are still under debate, the region has been the subject of intensive study with active and passive source seismic profiles and networks. A recurrent theme from these studies is that the high surface elevations are not mirrored by a thick crustal root, however the most recent crustal thickness estimates still differ by ~10 km. This difference has significant implications for mechanisms to explain the support of high topography in the region, specifically whether the surface elevation is isostatically balanced within the crust or support for the high elevations has to come from deeper in the Earth. Our project is an interdisciplinary collaboration to apply techniques developed by the team for shallow high-frequency seismic applications to lithospheric scale seismology. Specifically, we plan to use diffracted seismic waves, from earthquakes and from ambient seismic noise, to image the Moho (the seismic velocity contrast that can be identified with the crust-mantle boundary). Detection of Moho diffractions is to date limited to earthquakes and explosion sources. Our approach is to perform interstation crosscorrelations of previously recorded explosions and earthquakes and of ocean-generated ambient seismic noise to simulate a signal source at each station location. This technique would allow detection of Moho diffractions and therefore Moho mapping in areas where conventional techniques are not applicable.

该项目以两个问题为中心：1。是什么促进了科罗拉多州和新墨西哥州的落基山脉？表面高度是由于厚度厚，浮力的外壳而高的，还是地壳不比周围区域厚的地壳，而是坐在下面的平常地幔中，它支持了异常高的海拔高度？为了回答这个问题，我们必须绘制落基山脉下的地壳竖井边界。这样做的常规方法使得与地壳厚度有关。我们建议通过调查问题2来解决这一问题：我们可以使用最近开发的方法，该方法已成功地应用于浅地球物理问题，例如水文成像，以找到更深的地壳掩体边界？我们将使用已经收集的地震数据集并应用新的分析技术来对构造神秘区域的动态有限制。 南部落基山脉地区记录了大陆集会，远离板块边界的山区建筑的复杂历史以及初期的大陆裂谷。由于该大区域的提升的机制和时机仍在争论中，因此该地区一直是具有主动和被动源地震概况和网络的密集研究的主题。 这些研究的一个复发主题是，高表面高度不会被厚的地壳根反映，但是最近的地壳厚度估计值仍然有所不同约10 km。 这种差异对解释该地区高地形的支持的机制具有重要意义，特别是表面高度是否在地壳内同度平衡或对高升高的支持必须来自地球上的深处。 我们的项目是一种跨学科的合作，以应用团队开发的技术，用于岩石圈量表地震学浅层高频地震应用。具体而言，我们计划使用衍射的地震波，从地震到从环境地震噪声到成像Moho（可以通过外壳膜边界识别的地震速度对比度）。迄今为止，Moho衍射的检测仅限于地震和爆炸源。我们的方法是对先前记录的爆炸和地震以及海洋生成的环境地震噪声进行互相关，以模拟每个站点的信号源。该技术将允许检测Moho衍射，因此可以在不适用传统技术的区域中进行MOHO映射。