A hands-on guide for computing and exploring focal mechanisms in the North Sea for risk mitigation of large-scale CO2 injections.

The success of CCS depends heavily on understanding the present-day stress field to anticipate reservoir and cap rock response to fluid injection. Despite its importance, many proposed carbon storage sites in the North Sea are located in areas with little to no borehole stress data available, presenting a significant challenge. Within the ACT project SHARP Storage framework, we have addressed this gap by generating a comprehensive earthquake bulletin for the North Sea, revealing spatial clusters of seismic events with the majority of earthquakes with ML < 4. Focal mechanisms of earthquakes are excellent indicators of crustal dynamics, which are essential for assessing the present-day stress field. Therefore, to improve the understanding of the in-situ stress conditions, we created a comprehensive workflow to evaluate focal mechanisms based on data from the North Sea. This guide represents an explanation of the workflow, which was used to evaluate focal mechanisms of the earthquakes with a data of sufficient quality.

碳捕获与封存（Carbon Capture and Storage, CCS）的成功，在很大程度上依赖于对现今应力场的认知，以预测储层与盖层对流体注入的响应。尽管其重要性不言而喻，但北海地区众多候选碳存储场址均位于几乎无钻孔应力数据可用的区域，这带来了重大挑战。在ACT项目的SHARP Storage研究框架下，我们通过构建北海地区全面的地震目录填补了这一空白，结果揭示了地震事件的空间丛集特征，其中绝大多数地震的震级（ML）小于4。地震震源机制是反映地壳动力学的优质指标，而后者对评估现今应力场至关重要。因此，为加深对原位应力状况的认知，我们基于北海地区的相关数据构建了一套完整的震源机制评估工作流程。本指南即对该工作流程的详细说明，该流程被用于评估数据质量达标地震的震源机制。