Borehole Seismogram Calibration and Deconvolution for Ground Motion and Earthquake Source Studies: Applications to the ICDP-GONAF project in NW Turkey

在项目最初的1.5年期间，我们专注于分析ICDP-GONAF项目框架内的第一个垂直地震仪阵列的地震记录，该项目位于伊斯坦布尔东南部的图兹拉半岛。与地面台站相比，由于井下台站的低噪声条件和高信噪比，因此可以检测到许多地面阵列无法检测到的微地震（M<1）事件。在这里提出的扩展框架内，我们打算进一步扩大马尔马拉海东部的事件数据库，通过整合最近在Armutlu半岛完成的GONAF钻孔阵列（2014年夏季完成）以及目前钻探的另外四个阵列，这些阵列将于2015年春季投入使用（例如在王子群岛）。为了研究图兹拉地区的近地表特征，如速度结构和衰减，我们应用了几种不同的技术。将对新的GONAF站采用同样的方法，以评价我们在图兹拉场址的观测是否具有场址特殊性或是否也可转移到其他地质构造。不同地点的比较分析将对制定数据分析方案具有重要价值，该方案还可以校正地点效应，这是改进例如震源参数估计所需的程序。此外，我们计划将垂直地震剖面处理技术应用于马尔马拉海东部NAFZ断裂分支的断裂带成像。为此，我们将选择与GONAF台站震中距离20公里（深度范围5-20公里）内的当地地震活动，并使用不同深度的钻孔传感器。将研究首次部署在300 m深度的3分量1Hz MARK地震仪的波形记录，并有望为研究区域的剪切波特征提供新的见解。

During the initial 1.5-year period of the project we focused on analyzing seismic recordings from the first vertical seismometer array implemented in the frame of the ICDP-GONAF project, located on the Tuzla peninsula in SE Istanbul. Due to the low-noise conditions and resulting high signal-to-noise ratios at the downhole stations compared to surface stations it was possible to detect numerous microseismic (M<1) events which went undetected by surface arrays. In the frame of the here proposed extension we intend to further enlarge the event data base for the eastern Sea of Marmara by integrating additional recently completed GONAF borehole arrays on the Armutlu peninsula (completed in summer 2014) as well as up to four more arrays which are currently drilled and that shall be in operation by spring 2015 (e.g. on the Princes Islands). For the investigation of the near-surface properties at the Tuzla site such as the velocity structure and attenuation we applied several different techniques. The same methods will be applied to the new GONAF stations to evaluate whether our observations at the Tuzla site are site-specific or transferable also to other geological formations. The comparative analysis of different sites will be of great value for developing a data analysis scheme that also corrects for site effects, a procedure needed to improve for example earthquake source parameter estimations. Furthermore we plan to apply processing techniques from vertical seismic profiling for fault-zone imaging of the NAFZ fault branches below the eastern Sea of Marmara. To do so we will select local seismicity within 20 km epicentral distance (depth range 5-20km) to the GONAF stations and use the different depth levels of the borehole sensors. The waveform recordings of 3-component 1Hz MARK seismometers deployed at 300 m depth for the first time will be studied and are expected to provide new insights in shear-wave characteristics of the study area.