尼西羅斯島是南愛琴海火山弧（SAVA）最東端的活火山，位於以伸展構造為主的區域， 該構造是由非洲板塊俯衝到愛琴海微板塊之下形成的。 2021年，希臘統一地震台網絡 （HUSN）在尼西羅斯島西南近海區域記錄到一次群震，共1620次地震，其中包含46次 區域規模大於 4.0 的地震。為了研究驅動這次群震的原理，我們採用了結合地震重定 位、地震活動性遷移建模、頻率指數分析和矩張量反演的方法。雙差重定位結果顯示， 在5-20公里深度處存在一個密集的西南-東北走向的狹長群震，表明一條先前存在的、 未被探測的近海斷層已被喚醒。孔隙壓力擴散模型無法很好地模擬地震活動，而地震 活動性遷移分析顯示，地震傳播是由無震潛移（≈0.16 km/天）所引發的。頻率指數值 接近零，表示地震活動類型為混合型，發生在流體飽和介質中。同時，多個地震事件 的完整矩張量解均一致的顯示存在正的體積分量，暗示震源處有存在張性斷層的可能。 綜合證據支持流體來自尼西羅斯島西南部的岩漿體，引起了沿著一條既有的西南-東北 走向斷層的無震潛移，並導致了群震的發生。這些發現顯示流體-斷層交互作用在SAVA 火山構造地震活動中的重要性，尤其是有鑑於 2025 年聖托里尼-阿莫爾戈斯群震與尼 西羅斯群震具有一些共同特徵的情況下。;Nisyros， the easternmost active volcano of the South Aegean Volcanic Arc (SAVA)， is located in a predominantly extensional tectonic regime resulting from the subduction of the African plate beneath the Aegean microplate. In 2021， a seismic swarm comprising 1，620 events， including 46 earthquakes with local magnitudes above 4.0， was recorded by the Hellenic Unified Seismic Network (HUSN) in the offshore area southwest of Nisyros. To investigate the driving mechanism of this swarm， we follow an approach combining earthquake relocation， seismicity migration modelling， frequency index analysis， and moment tensor inversion. Double-difference relocation reveals a compact SW–NE elongated cluster at 5–20 km depth， suggesting activation of a pre-existing unmapped offshore fault. Pore-pressure diffusion models fail to produce a good fit， whereas analysis of seismicity migration indicates propagation driven by aseismic slip (≈0.16 km/day). Frequency index values are near zero， suggesting hybrid-type seismicity within a fluid-saturated medium， while full moment tensor solutions of several events consistently require a positive volumetric component， suggestive of tensile faulting at the source. The combined evidence supports fluids sourced from a magmatic body southwest of Nisyros， initiating aseismic slip along a pre-existing SW–NE fault and driving the swarm. These findings highlight the role of fluid–fault interactions in SAVA volcano-tectonic seismicity， especially in light of the recent 2025 Santorini-Amorgos swarm， which shared some common features with the Nisyros swarm.
