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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/88185

    Title: Crustal Seismicity of the eastern Hellenic volcanic arc: Its relationship with active faulting and volcanic centers
    Authors: 安拉蕊;Andinisari, Ratri
    Contributors: 地球科學學系
    Keywords: 愛琴海;地殼地震;流體;矩張量;地震危險;Aegean;crustal earthquake;fluids;moment tensor;seismic hazard
    Date: 2022-01-24
    Issue Date: 2022-07-13 18:27:16 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 愛琴海下方非洲板塊的隱沒形成了希臘隱沒帶和火山弧,控制著愛琴海南部的地震活動,包括愛琴海東南部和聖托里尼-阿莫爾戈斯帶。 由於存在活動斷層和各種變形地形,這些地區還受到非洲板塊回滾引起的伸展變形的影響。 因此,此論文旨在確定這些活動斷層和火山中心如何塑造觀測到的地殼地震活動。 由於這些地區發生了中大型地殼地震(Mw>6),我們還對繪製的活動斷層的潛勢進行了評估。
    2002年到2020年間,被臨時和永久地震測震網所記錄的地震運動,我們藉著最小一維速度模型重新定位,以獲得精確的相對位置。 在愛琴海東南部,這些位置能夠描繪出大部分活動斷層。 另一方面,沿聖托里尼-阿莫爾戈斯帶重新定位的地震活動只能描繪出八個活動斷層中的三個,表示這些活動可能不僅僅是由活動斷層引起的。相反地,重新定位的地震分佈也告訴了我們安德羅斯島和聖托里尼-阿莫爾戈斯東北部段下方的兩個垂直地震群,可能是向上遷移流體的通道。
    岩石物理參數的側向分佈和全矩張量解後來被用來確定地殼地震活動與沿聖托里尼-阿莫爾戈斯帶的流體之間的關係。在垂直地震群位置發現的高 Vp/Vs 比 (1.77-1.86)、裂縫密度 (0.15-0.30) 和流體飽和度 (0.71-0.76) 顯示存在流體並加強了這些結構確實可能存在的可能性與向上的流體遷移有關。發生在 Kolumbo 海底火山和 Anydros 島下方的微地震,藉由 P 波極性和 SV/P、SH/P 振幅比的矩張量反演,指出指出矩張量解和非雙耦合有正相關分量。這暗示微地震可能是由流體運移過程中裂縫的開合所產生的拉伸斷層引起的。
    地震危害度評估是通過利用考慮了孕震層厚度的經驗關係來估計每個活動斷層的預期地震規模來進行的。 研究區發孕層厚度為12.1~15.4km。 兩個地區斷層未來地震的預期的地震矩規模在5.9-7.2之間。 由於這些斷層大多位於外海,由這些外海斷層中的任何一個破裂引起的主震都可能伴隨著海嘯。;The subduction of the African plate beneath the Aegean has formed the Hellenic subduction zone that controls the seismicity across the southern Aegean, including SE Aegean and the Santorini-Amorgos zone. These areas are also affected by extensional deformation due to the slab rollback of the African lithosphere that is evidenced by the existence of active faults and a variety of deforming terrains. Therefore, this thesis aims to determine how these active faults and volcanic centers shape the observed crustal seismicity. Since moderate to large crustal earthquakes (Mw>6) have occurred previously in these areas, this thesis also assesses the potential seismic hazard with respect to the mapped active faults.
    The crustal events recorded by temporary and permanent seismic networks from 2002 to 2020 were relocated by using minimum 1D velocity models to obtain precise relative locations. In SE Aegean, these locations were able to delineate most of the active faults. On the other hand, the relocated crustal events along the Santorini-Amorgos zone could only delineate three out of eight active faults, indicating that these events may not be caused solely by active faulting. Instead, the relocated crustal events revealed two vertical clusters of earthquake beneath the island of Anydros and the NE segment of Santorini-Amorgos that may be pathways of upward migrating fluids.
    Lateral distributions of petrophysical parameters and full moment tensor solutions for the well-constrained events were later used to determine the relationship between crustal seismicity and fluids along the Santorini-Amorgos zone. High Vp/Vs ratios (1.77-1.86), crack density (0.15-0.30), and fluid saturation (0.71-0.76) found at the locations of the vertical earthquake clusters indicate the existence of fluids and strengthened the possibility that these structures may indeed be related to upward fluid migration. The moment tensor inversion of P-wave polarities and SV/P, SH/P amplitude ratios for microearthquakes that occurred beneath Kolumbo submarine volcano and Anydros island resulted in moment tensor solutions with positively correlated non-DC components. This signifies that the microearthquakes may be caused by tensile faulting generated by the opening and closing of cracks during the fluid migration.
    The seismic hazard assessment was performed by utilizing empirical relationships that take into account the seismogenic layer thickness to estimate expected earthquake magnitude of each active fault. The seismogenic layer thickness of the study areas is ranging from 12.1 km to 15.4 km. Expected moment magnitudes of future earthquakes of the faults in both areas vary between 5.9-7.2. Since these faults are mostly located offshore, a mainshock caused by the rupture of any of these offshore faults may be followed by a tsunami.
    Appears in Collections:[地球物理研究所] 博碩士論文

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