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

皮托深渊的重力：复活节微板上传播的裂谷尖端

• 批准号: 9000435
• 负责人: Fernando Martinez
• 金额: $ 5.21万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-04-01 至 1991-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9000435&HistoricalAwards=false
• 关键词: Gravity; Pito; Deep; Propagating; Rift

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.

对沿东太平洋海隆 (EPR) 95.5W 的传播扩散中心进行的详细调查表明，板块边界配置不是静态的，而是可以经历复杂的几何变化。 基于地壳和地幔内的动态、运动学或机械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，Martinez 博士将通过检查 EPR 上 23S 之前从 Pito Deep 区域获取的数据来对各种模型进行评估。 该区域在几个方面与 95.5 传播器形成对比：Pito Deep 传播器沿着宽阔的“前沿”前进，而不是像 95.5N 那样沿着“尖端”前进； 当地地形变化很大，从区域平均3500m到局部洼地5980m； 裂谷以北的复杂地形模仿了裂谷带的结构和趋势，表明该地区存在异常强烈的耦合。 任何或所有这些对比都可以用以下事实来解释：Pito Deep 沿着长距离（95.5N 处的特征为 300 公里与 30 公里）偏移并侵入异常古老的岩石圈（3 my vs 1 my）。 Martinez 博士将对现有的 SeaMARCII 测深数据进行网格化，并构建 Pito Deep 区域的地形校正布格异常图。 有了这个，并假设均衡补偿的性质，他将计算残余重力异常，以识别莫霍面地形引起的异常。 此过程后留下的异常将构成竞争模型之间测试的基础，这些模型需要：1）软流圈中的粘性流，2）由于岩脉侵入引起的热效应，或3）有限强度岩石圈的机械影响。