Historical seismic catalogs report that the Gargano Promontory (southern Italy) was affected in the past by earthquakes with medium to high estimated magnitude. From the instrumental seismicity, it can be identified the most energetic Apulian sequence which occurred in 1995 with a main shock of MW=5.2 followed by about 200 aftershocks with maximum magnitude 3.7. The most energetic earthquakes of the past are attributed to right-lateral strike-slip faults, while there is evidence that the present-day seismicity occur on thrust or thrust-strike faults. In this paper, we show a detailed study on focal mechanisms and stress field obtained by micro-seismicity recorded from April 2013 until the present time in the Gargano Promontory and surrounding regions. Seismic waveforms are collected from the OTRIONS Seismic Network (OSN), from the Italian National Seismic Network (RSN) and integrated with data from the Italian National Accelerometric Network (RAN) in order to provide a robust dataset of earthquake localizations and focal mechanisms. The effect of uncertainties of the velocity model on fault plane solutions has been also evaluated indicating the robustness of the results. The computed stress field indicates a deep compressive faulting with maximum horizontal compressive stress, SHmax, trending NW-SE. The seismicity pattern analysis indicates that the whole crust is seismically involved up to a depth of 40 km and indicates the presence of a low angle seismogenic surface trending SW-NE and dipping SE-NW, similarly to the Gargano-Dubrovnik Fault . Shallower events, along the eastern sector of the Mattinata Fault, are W-E dextral strike-slip fault. Therefore, we hypothesized that the seismicity is locally facilitated by preexisting multidirectional fractures, confirmed by the heterogeneity of focal mechanisms and explained by the different reactivation processes in opposite directions over the time, involving the Mattinata shear zone.

中文翻译：

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基于微地震分析的加尔加诺海角（意大利南部）的地震成因结构取向和应力场

历史地震目录报告说，加尔加诺海角（意大利南部）过去曾受到中等至高估计地震的影响。从仪器的地震活动性来看，可以确定出最有活力的阿普利亚层序，该序列发生在1995年，主震为MW = 5.2，随后是大约200次余震，最大震级为3.7。过去最活跃的地震归因于右侧走滑断层，而有证据表明，当今的地震活动发生在逆冲断层或逆冲断层断层上。在本文中，我们将详细研究2013年4月至今在加尔加诺海角及周边地区通过微地震获得的震源机制和应力场。地震波形是从OTRIONS地震网络（OSN）收集的，来自意大利国家地震台网（RSN）的数据，并与来自意大利国家加速度计网（RAN）的数据集成，以提供可靠的地震定位和震源机制数据集。还评估了速度模型的不确定性对断层平面解的影响，表明了结果的鲁棒性。计算出的应力场指示出深压缩断裂，其最大水平压缩应力SHmax呈NW-SE趋势。地震活动模式分析表明，整个地壳在地震作用下一直延伸到40 km的深度，并表明存在一个类似于Gargano-Dubrovnik断层的低角度成地震表面，其趋势为SW-NE和SE-NW倾角。沿着Mattinata断层东部的浅层事件是WE右旋走滑断层。所以，