The region around the Mejillones Peninsula is characterized by major onshore and offshore fault systems. The existence of major splay faults in these fault systems has been debated. To improve our undestanding of seismotectonic processes affecting the MP, we built a new catalog of aftershocks of the 1995 Antofagasta earthquake (Mw 8.1) recorded by the CINCA seismic network. In addition, we build a three-dimensional tomographic model to determine the physical properties of the upper plate using arrival times from our new catalog combined with other earthquakes catalogs derived from several networks deployments across the MP. We detected seismicity in the outer wedge of the upper plate. The seismicity is partially defined by a clear lineament between 22 and 5 km depth that we defined as a splay fault. The focal mechanisms indicate a rupture plane with NE orientation and SE dip. The seismicity in the upper plate and splay fault are located in the areas in which the Vp and Vs velocities are decreased and the Vp/Vs ratio is increased, suggesting a fractured fault zone within the outer wedge of the upper plate. We propose the presence of fluids in the fracture fault zone within the outer wedge because the decrease in Vs larger than that of Vp and repeating earthquakes clusters were detected. Our observations present clear evidence of the activation of the splay fault in the outer wedge of the North Chilean offshore forearc.

Mejillones半岛周围地区的特点是主要的陆上和海上断层系统。在这些断层系统中是否存在主要的张开断层已经引起了争论。为了改善对影响MP的地震构造过程的不了解，我们建立了CINCA地震网络记录的1995年安托法加斯塔地震（Mw 8.1）余震的新目录。此外，我们建立了一个三维断层扫描模型，利用新目录的到达时间以及从跨MP的多个网络部署获得的其他地震目录，来确定上板的物理特性。我们在上板的外楔中检测到地震。地震活动部分由深度在22 km和5 km之间的清晰线条定义，我们将其定义为张开断层。震源机制表明破裂面具有NE方向和SE倾角。上板的地震活动性和张裂断层位于Vp和Vs速度降低且Vp / Vs比率增加的区域，表明上板外楔形内有断裂断层带。我们建议在外楔形内的断裂断层带中存在流体，因为检测到Vs的减小大于Vp的减小和重复地震群。我们的观察结果清楚地表明了北智利近海前臂外楔上的张开断层被激活。这表明在上板的外楔形区域内有一个断裂的断裂带。我们建议在外楔形内的断裂断层带中存在流体，因为检测到Vs的减小大于Vp的减小和重复地震群。我们的观察结果清楚地表明了北智利近海前臂外楔上的张开断层被激活。这表明在上板的外楔形区域内有一个断裂的断裂带。我们建议在外楔形内的断裂断层带中存在流体，因为检测到Vs的减小大于Vp的减小和重复地震群。我们的观察结果清楚地表明了北智利近海前臂外楔上的张开断层被激活。