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

对沿东太平洋海隆(EPR)95.5W传播的扩展中心的详细调查表明，板块边界构型不是静态的，而是可以经历复杂的几何变化。基于地壳和地幔内的动力学、运动学或力学过程的模型已经被开发出来解释这些错综复杂的情况。然而，这些模型对其他传播系统的适用性还有待确定，马丁内斯博士将通过检查之前在EPR上23秒从皮托深区获得的数据，对各种模型进行评估。这一地区与95.5传播者在几个方面形成了鲜明的对比：皮托深度传播者沿着宽阔的“锋面”前进，而不是北纬95.5度的“尖端”；局部地形差异很大，从区域平均值3500米到局部凹陷5980米不等；裂谷以北的复杂地形模拟了裂谷地带的组构和趋势，表明该地区存在异常强烈的耦合。这些约束中的任何一种或全部都可以用以下事实来解释：Pito Deep沿着一条长的(300公里对95.5北纬30公里)转换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水深测量进行网格划分，并构建一张经过地形校正的皮托深部地区的布格异常图。在此基础上，并假设均衡补偿的性质，他将计算剩余重力异常，以识别莫霍面地形造成的异常。这一过程后留下的异常将成为相互竞争的模型之间进行测试的基础，这些模型需要：1)软流层中的粘性流动，2)由于堤坝入侵而产生的热效应，或3)有限强度的岩石圈的力学含义。

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.