Ligurian Ocean Bottom Seismology and Tectonics Research (LOBSTER)

SPP 4D-MB内拟议的龙虾活动区的目的有两个：1)在利古里亚海部署一个法国/德国海底地震仪网络，作为阿尔普阵列地震网络的海洋组成部分；2)校正和处理海洋数据，以便与陆上数据兼容。阿尔普阵列是一项欧洲倡议，旨在部署数百台分布紧密的宽带地震仪，覆盖整个阿尔卑斯山造山带，以提供最先进的地下结构成像。SPP 4D-MB和AlpArray的海上部分涉及在利古里亚海部署来自法国/德国的33个宽带OBS。德国站的部署在这里申请。为此，法国的同事们已经争取到了2017年的船期进行部署。与此同时，德国提交了一份船舶时间提案，并为2018年春季在RV Meteor/Merian上批准了14天的船舶时间，用于仪器回收，以在两国之间分担与船舶有关的费用。OBS记录对于确定从西阿尔卑斯山向亚平宁山脉过渡时的地下结构和提高我们对该系统的三维几何及其运动学的理解将是必不可少的。OBS是先进的仪器系统，由于其海底操作环境的原因，其操作和由此产生的原始数据与陆上对应的系统有很大差异。由于这些根本性的差异，龙虾的主要任务是提供与陆上数据兼容的OBS数据。在战略规划4D-MB框架内，对陆上和近海数据进行综合分析需要及时更正和提供海洋数据，以便能够合并这两个数据集。因此，在回收仪器之前必须准备和设置多个处理步骤，以便在回收巡航期间数据可用时立即开始工作。部署和恢复巡航之间的时间应用于这一筹备阶段。第一处理步骤涉及仪器时钟误差校正。由于没有与外部世界的连接，OBS无法与标准的定时系统保持同步(通过GPS或网络连接)。环境地震噪声的互相关分析为非线性时钟漂移校正提供了技术。OBS以自由落体模式远程部署，无需干预--因此，它们在海底的实际水平方向未知。因此，OBS的水平方向必须根据测量的气枪射击和/或环境噪声互相关来确定。在项目的最后一步，我们将通过功率谱密度的概率密度函数来表征OBS数据的频谱行为，这将为Liguria海地震噪声的产生和传播提供深入的见解。

The aim of the proposed LOBSTER activity field within SPP 4D-MB is twofold: 1) to deploy a network of French/German ocean bottom seismometers (OBS) in the Ligurian Sea to serve as the marine component of the seismic network of AlpArray, and 2) to correct and process the marine data in order to be compatible with onshore data. AlpArray is a European initiative with the aim to deploy several hundred closely spaced broadband seismometers that will cover the entire Alpine orogen to provide state-of-the-art imaging of subsurface structures. The offshore component of SPP 4D-MB and AlpArray involves deployment of 33 broadband OBS from France/Germany in the Ligurian Sea. The deployment of the German stations is applied for here. To this end, colleagues in France have secured ship time in 2017 for the deployment. Simultenously, a ship time proposal has been submitted in Germany and 14 days of ship time have been granted on RV Meteor/Merian for the spring of 2018 for instrument recovery in order to share ship-related costs between the two nations. OBS recordings will be essential to define subsurface structures at the transition from the Western Alps to the Apennines and improve our understanding of the 3D-geometry of the system and its kinematics. OBS are advanced instrument systems that, as a result of their subsea operating environment, differ significantly in their operation and resultant raw data from their land-based counterparts. As a result of these fundamental differences, the main task of LOBSTER is to provide OBS data compatible with onshore data. Within the framework of SPP 4D-MB a combined analysis of onshore and offshore data requires the timely correction and provision of the marine data so that the two data sets can be merged. As a consequence, a number of processing steps must be prepared and set up prior to instrument recovery so that the work may commence as soon as the data become available during the recovery cruise. The period between the deployment and recovery cruises shall be used for this preparatory phase. The first processing step involves instrumental clock error correction. With no connection to the outside world, OBS are not able to maintain synchronization with standard timing systems (via GPS or network connection). Analysis of the cross correlation of ambient seismic noise provide techniques for nonlinear clock drift corrections. OBS are deployed remotely and without intervention in a free-fall mode - therefore, their actual horizontal orientation on the seafloor is unknown. Consequently, horizontal orientation of the OBS must be determined from measured air gun shots and/or ambient noise cross correlation. In the last step of the project we will characterize the spectral behaviour of the OBS data through probability density functions of power spectral density, which provide insights on the generation and propagating of seismic noise in the Liguria Sea.