High Resolution Imaging of Mantle Discontinuities across South America at 20 Degrees South

南美洲南纬 20 度处地幔不连续性的高分辨率成像

• 批准号: 0001000
• 负责人: Kelly Liu
• 金额: $ 6.34万
• 依托单位: Kansas State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-15 至 2002-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0001000&HistoricalAwards=false
• 关键词: Resolution; Imaging; Mantle; Discontinuities; across

Kelly LiuEAR-0001000This proposal will conduct a high resolution study of the major discontinuities beneath a 3000 km long profile along the 20 degree S latitude line across central South America. The study will utilize a unique data set, which is a combination of broadband data sets from three portable seismic experiments conducted during 1992-1995. Preliminary results by non-linear stacking of 752 high quality radial receiver functions suggest clear spatial variations of both the 410 and 660 discontinuities across the profile. Some interesting features include: 1) the 660 discontinuity is depressed by at least 35 km, or as large as 65 km, by the subducting slab, 2) west of the Andes, the depth to the Moho is about 40-45 km, but it increases to 65-80 km over a distance of less than 50 km and decreases to about 45-50 km beneath the eastern boundary of the Andes, 3) the transition zone thickness is about 250 km of the ocean side, and 260 km on the continent side, indicating that the former is hotter than the later, and 4) there exists a group of strong negative arrivals above the 300 km depth, but only above the slab on the continental side. The study will use a set of procedures such as phasing depth imaging of P-to-S and S-to-P conversions, conversions of waves from deep local earthquakes at discontinuities, and synthetic seismogram to improve and expand the preliminary results, and to measure the spatial variations of other properties of the discontinuities such as their sharpness and velcoity contrast. The research will develop a procedure to stack converted waves from tilted interfaces to directly map the subducting slab.

Kelly Liujiang-0001000本提案将对横跨南美洲中部的南纬20度线上沿着3000 km长剖面下的主要不连续面进行高分辨率研究。 这项研究将利用一套独特的数据，这套数据是1992-1995年期间进行的三次便携式地震试验的宽带数据的组合。 752个高质量径向接收函数的非线性叠加的初步结果表明，在剖面上410和660个不连续点都有明显的空间变化。 一些有趣的功能包括：（1）660不连续面被俯冲板片压下至少35 km，最大可达65 km;（2）在安第斯山脉以西，莫霍面的深度约为40-45 km，但在不到50 km的距离上，莫霍面的深度增加到65-80 km，并在安第斯山脉东边界以下减小到45-50 km，（3）过渡带厚度在大洋侧约为250 km，在大陆侧约为260 km，表明前者比后者热;（4）在300 km深度以上存在一组强负波至，但仅在大陆侧板片之上。 该研究将使用一套程序，如P-to-S和S-to-P转换的相位深度成像，从不连续面处的深层本地地震波的转换，以及合成地震记录，以改进和扩展初步结果，并测量不连续面的其他属性的空间变化，如它们的锐度和速度对比度。 本研究将发展一套从倾斜界面叠加转换波的程序，以直接映射俯冲板片。