Gravity of Pito Deep: A Propagating Rift Tip on the Easter Microplate

对东太平洋隆起（EPR） 95.5W处扩张中心的详细观测表明，板块边界构型不是静态的，而是可以经历复杂的几何变化。基于地壳和地幔内部的动力学、运动学或力学过程的模型已经被开发出来来解释这些错综复杂的现象。然而，这些模型对其他传播系统的适用性尚未确定，马丁内斯博士将通过检查EPR上23S Pito Deep地区先前获得的数据，对各种模型进行评估。这个区域与95.5传播体在几个方面形成对比：皮托深传播体沿着一个宽阔的“锋面”前进，而不是像95.5 n那样的“尖端”；当地地形变化很大，从区域平均值3500米到局部洼地5980米；裂谷北部的复杂地形模拟了裂谷带的结构和走向，表明该地区存在异常强烈的耦合。这些对比中的任何一种或全部都可以用以下事实来解释：皮托深沿一条长（95.5北纬300公里对30公里）的变形偏移，并侵入异常古老的岩石圈（3my对1my）。马丁内斯博士将对现有的SeaMARCII测深系统进行网格化，并构建皮托深区经过地形校正的布格异常图。利用这一点和均衡补偿性质的假设，他将计算剩余重力异常，以识别由于莫霍地形引起的异常。在这一过程之后留下的异常将成为测试竞争模型的基础，这些模型需要：1)软流圈中的粘性流动，2)岩脉侵入引起的热效应，或3)有限强度岩石圈的机械含义。

Detailed surveys of a propagating spreading center along the East Pacific Rise (EPR) at 95.5W show that plate boundary configurations, rather than being static, can undergo complex geometric changes. Models based on either dynamic, kinematic or mechanical processes within the crust and mantle have been developed to explain these intricacies. However, the applicability of these models to other propagating systems has yet to be established, and Dr. Martinez will conduct an evaluation of the various models by examining previously acquired data from the Pito Deep area at 23S on the EPR. This area contrasts with the 95.5 propagator in severval ways: the Pito Deep propagator is advancing along a broad "front", not a "tip" as at 95.5N; local topography varies enormously from a regional mean of 3500m to a local depression of 5980m; and complex topography north of the rift mimics the fabric and trend of the rift zone, suggesting an unusually strong coupling across this region. Any or all of these constrasts may be explained by the fact that Pito Deep is offset along a long (300 km vs 30 km for the feature at 95.5N) transform and intrudes into unusually old lithosphere (3 my vs 1 my). Dr. Martinez will grid existing SeaMARCII bathymetry and construct a terrain-corrected Bouger anomaly map of the Pito Deep region. With this and with assumptions of the nature of isostatic compensation he will calculate residual gravity anomalies to identify anomalies due to Moho topography. Anomalies that remain after this procedure will form the basis for testing among the competing models that require either: 1) viscous flow in the asthenosphere, 2) thermal effects due to dike intrusion, or 3) mechanical implications of a lithosphere of finite strength.