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Fault slip rates, constancy of seismic strain release, and landscape evolution in the eastern California shear zone.

机译:断层滑动率,地震应变释放的恒定性和东部加利福尼亚剪切带的景观演化。

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摘要

The constancy of strain accumulation and release in time and space is one of the most fundamental issues in tectonics. Models of geodetic data suggest the Death Valley-Fish Lake Valley fault zone (DV-FLVFZ) is storing most of the Pacific-North American plate boundary strain in the northern eastern California shear zone (ECSZ). However, the scarcity of geochronologically constrained slip rates on the DV-FLVFZ has made it difficult to determine whether strain storage and release are constant in this region. I used airborne laser swath mapping (ALSM) digital topographic data to restore offset alluvial fans to their pre-faulting positions, combined with cosmogenic 10Be and 36Cl geochronology to determine slip rates along the DV-FLVFZ.; Offset measurements combined with cosmogenic nuclide geochronology yields a slip rate of ∼4.5 mm/yr for the DV-FLVFZ in northern Death Valley. Summing this rate with known rates on the major faults at similar latitudes suggests a late-Pleistocene geologic slip budget across the northern ECSZ of 8.5 to 10 mm/yr. This rate agrees with the geodetic rate and implies the strain transient in the southern ECSZ does not extend away from the structurally complex zone near the Big Bend of the San Andreas fault.; Combining offset measurements for two alluvial fans in Fish Lake Valley with 10Be ages yields late Pleistocene rates of ∼2.5 mm/yr and ∼3 mm/yr for the northern DV-FLVFZ. These rates are slower than those determined for the system in Death Valley, indicating rates decrease northward. These data suggest that at ∼37.5°N latitude, significant deformation must be accommodated on structures east of Fish Lake Valley, or strain accumulation and release rates have not remained constant through time.; Furthermore, comparison of surface roughness values derived from the ALSM data shows that eight mapped alluvial fans are statistically unique at the 99% confidence level. The roughness metric indicates that fans become smoother from the active channel to a surface dated at 70 ka. Beyond 70 ky, alluvial landforms become rougher with age, suggesting that fans in arid regions smooth out with time until a threshold is crossed where roughness increases with age due to headward tributary incision.
机译:应变在时间和空间上的积累和释放的恒定性是构造学中最基本的问题之一。大地测量数据模型表明,死亡谷-鱼湖谷断层带(DV-FLVFZ)在加利福尼亚北部的剪切带(ECSZ)中存储了太平洋-北美板块的大部分边界应变。但是,DV-FLVFZ缺乏按时间顺序排列的受滑移率限制,因此很难确定该区域的应变存储和释放是否恒定。我使用机载激光测绘测绘(ALSM)数字地形数据将偏移冲积扇恢复到其断层前的位置,并结合宇宙成因的10Be和36Cl年代学来确定沿DV-FLVFZ的滑移率。偏移量测量与宇宙成因核素年代学相结合得出的死亡谷北部DV-FLVFZ滑移率约为4.5 mm / yr。用类似纬度的主要断层上的已知比率求和,这表明整个ECSZ北部的晚更新世地质滑动预算为8.5至10 mm / yr。该速率与大地测量速率一致,并暗示在ECSZ南部的应变瞬变不会远离San Andreas断层大弯附近的结构复杂区域。结合鱼类湖谷的两个冲积扇的偏移量测和10Be年龄,得出DV-FLVFZ北部的晚更新世速率约为2.5毫米/年,约为3毫米/年。这些速率比为死亡谷的系统确定的速率慢,表明速率向北降低。这些数据表明,在约37.5°N的北纬,鱼湖谷以东的结构必须承受明显的变形,否则应变的积累和释放速率不会随时间保持恒定。此外,从ALSM数据得出的表面粗糙度值的比较显示,在99%的置信度下,八个映射的冲积扇在统计上是唯一的。粗糙度度量表明风扇从活动通道到70 ka的表面变得更平滑。超过70 ky时,冲积地貌会随着年龄的增长而变得更粗糙,这表明干旱地区的粉丝会随着时间的流逝而平滑,直到越过阈值为止,由于朝前的支流切口,粗糙度随着年龄的增长而增加。

著录项

  • 作者

    Frankel, Kurt Lang.;

  • 作者单位

    University of Southern California.$bGeological Sciences: Doctor of Philosophy.;

  • 授予单位 University of Southern California.$bGeological Sciences: Doctor of Philosophy.;
  • 学科 Geology.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 193 p.
  • 总页数 193
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 P5;
  • 关键词

  • 入库时间 2022-08-17 11:39:44

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