A late Quaternary extension rate in the Taupo Volcanic Zone, New Zealand, derived from fault slip data
A late Quaternary extension rate in the Taupo Volcanic Zone, New Zealand, derived from fault slip data
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根据断层滑移数据得出新西兰陶波火山带的晚第四纪伸展率
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发表时间：
2001
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通讯作者：
K. Berryman
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作者：
P. Villamor;K. Berryman
摘要断层作用产生的西北-东南向伸展速率的时间平均周期为c。50 000年（10 000 - 64 000年），横跨Ngakuru-Waikite凹陷（现代陶波断层带，陶波火山带中部），最佳估计为1.9毫米/年（在1.2 - 2.8毫米/年的范围内），但在孕震深度为6 - 10公里时，最佳估计值为6.4毫米/年（范围为3.6 - 10.2毫米/年）。我们通过将已知年龄表面上断层位移的垂直分量相加，或将已知年龄地层单元中位移的垂直分量相加，在14 km宽的活动正断层带内，得到这一结果。我们通过估计地表和孕震深度处可能的断层面倾角范围，将7.2 ± 0.4 mm/年的垂直滑动速率总和转换为倾斜滑动位移速率和西北-东南延伸。在大地震中，孕震深度处的断层位移平均是地表的1.6倍，对于A/6.8或更小的地震震级，现代陶波断层带中整个古登堡-里克特地震分布所发生的位移中约有三分之一不会破裂到地表。断层倾角平均值C。在近地表为75 °，但在陶波断层带的孕震深度约束较差。从各种地方和文献的考虑，我们提出了一个倾角的c。在陶波断层带的孕震深度为60 °。我们的观察表明，表面的延伸只有很小的一部分（c。5%）是由小规模的断层低于我们的观察阈值0.1 - 0.5米的断层滑动。梭4.5孕震深度与地表之间的伸展速率之差为mm/yr，可能代表了伸展断裂张开和穿透性颗粒尺度伸展变形共同作用的地表伸展速率。
Abstract A northwest‐southeast oriented extension rate from faulting for a time‐averaged period of c. 50 000 yr (10 000–64 000 yr), across the Ngakuru‐Waikite depression (modern Taupo Fault Belt, central Taupo Volcanic Zone), has a best estimate of 1.9 mm/yr (in a range of 1.2–2.8 mm/ yr) in the near surface, but increases to a best estimate of 6.4 mm/yr (in a range of 3.6–10.2 mm/yr) at seismogenic depths of 6–10 km. We obtain this result by summing the vertical components of fault displacement across known‐age surfaces, or as the vertical component of displacement in stratigraphic units of known age, within the 14 km wide zone of active normal faulting. We convert the summed vertical slip rate of 7.2 ± 0.4 mm/yr to dip‐slip displacement rate and to northwest‐southeast extension by estimating a range of possible fault plane dips at the surface and at seismogenic depth. Fault displacement at seismogenic depth in large events is on average 1.6 times larger than at the surface, and for earthquake magnitudes of A/6.8 and smaller, about one‐third of the displacement occurring with the whole Gutenburg & Richter distribution of earthquakes in the modern Taupo Fault Belt will not rupture to the ground surface. Fault dip averages c. 75° in the near surface, but is poorly constrained at seismogenic depth in the Taupo Fault Belt. From a variety of local and literature considerations, we propose a dip of c. 60° at seismogenic depth in the Taupo Fault Belt. Our observations suggest only a minor component of extension at the surface (c. 5%) is contributed by small scale faulting below our observation threshold of 0.1–0.5 m of fault slip. The c. 4.5 mm/yr difference in extension rate between seismogenic depth and the ground surface may represent the surface extension rate caused by a combination of opening of extension fractures and penetrative grain‐scale extensional deformation.