ABSTRACT We present a high-precision gravity survey of the Whataroa River valley near the DFDP-2 drill site. We measured 466 new sites and achieved a standard error on repeat measurements of 0.015 mGal. We combined existing data from 134 sites. A negative residual gravity anomaly of up to 6 mGal is interpreted as a buried glacial channel 350–450 m beneath the valley floor. It is apparently dextrally offset and upthrown to the southeast by the Alpine Fault. We are able to better constrain the surface trace location of the Alpine Fault by combining gravity models with surface mapping. A high horizontal gravity gradient near the DFDP-2 drill site requires a steeply-dipping or overhanging bedrock surface, and indicates that an active reverse fault might bound the base of the hillslope. A 4 mGal residual gravity minimum near the axis of the valley near the DFDP-2 drill site is interpreted as the deepest point upstream of the fault of what was a lake that formed at the end of the Last Glacial Maximum (∼18 ka).

中文翻译：

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新西兰南岛 Whataroa DFDP-2 钻探场附近的中央高山断层重力测量

摘要 我们介绍了对 DFDP-2 钻探场附近 Whataroa 河谷的高精度重力测量。我们测量了 466 个新位点，重复测量的标准误差为 0.015 mGal。我们结合了 134 个站点的现有数据。高达 6 mGal 的负残余重力异常被解释为谷底下方 350-450 m 处的掩埋冰川通道。它显然被阿尔卑斯断层向右偏移并向上抛向东南方。通过将重力模型与表面映射相结合，我们能够更好地约束高山断层的表面轨迹位置。DFDP-2 钻场附近的高水平重力梯度需要陡倾或悬垂的基岩表面，这表明活动的反向断层可能会限制山坡的底部。