2017-08-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/691634摘要：中深層地震的發生機制仍存在爭議，雖然科學家早已觀察到世界各地隱沒帶有沿板塊向下伸張與向下壓縮的變化，且認為跟板塊隱沒深度有關，但真正的原因至今仍然不是很明確。琉球隱沒帶的地震活動最深大約是300公里，其北段是以向下伸張的地震為主，而向台灣延伸的南段卻是相反的向下壓縮。靠近台灣東北外海的琉球隱沒帶是研究俯衝板塊內應力轉換的絕佳地點之一，受到歐亞邊緣的影響，在此西邊的隱沒正要停止作用，中深層地震之震源機制可以指出板塊應力在150至300公里之間的哪個位置開始發生轉變，尤其是利用近期於2008年後所發生的中大型中深層地震，檢驗地震應力或斷層面是否與雙地震帶構造有關，以及是否可能發生在原位於外緣壟起的化石斷層上。本計畫將使用台灣及日本的寬頻網測站分析範圍在125&ordm;E以西的中深層震源機制，目的是建構琉球島弧下方之隱沒板塊的三圍構造及應力分布情形。藉由探索地震之P及T軸在瓦班氏地震帶中的系統性變化、對比預估的板塊熱參數及板塊年齡等資訊，我們試著了解菲律賓板塊內部應力變化的可能影響因子(靜態與動態)及他們之間的相對重要性。<br> Abstract: The causes of intermediate-depth earthquakes are in debate. The reasons for observed stress in different regions of subduction zones that varies from down-dip compression to down-dip extension remain unclear, although depth of slab penetration is apparently related. The Ryukyu subduction zone, with deepest seismicity around 300 km, is dominant in down-dip extension in northern segment, but down-dip compression in the southern segment toward Taiwan. The Ryukyu subduction zone northeast of Taiwan is one of the best places to study the stress transition in descending oceanic slab where subduction is terminating and switches of stress at depth between depth 150 and 300 km are likely resolvable using focal mechanisms, especially with those events occurred after 2008. It is also possible to associate those earthquakes with the double seismic zone and/or the fossil faults formed in outer-rise prior to subduction. In this proposal we plan to determine the focal mechanisms of intermediate-depth earthquakes using broadband waveforms recorded by arrays in Taiwan and Japan. The purpose is to constrain the stress pattern within the 3D slab beneath the southern Ryukyu arc west of latitude about 125&ordm;E. By exploring the systematic variations of P- and T-axis along the 3D slab defined by Wadati-Benioff zone seismicity, and with the estimated thermal parameter of the slab, we try to understand the relative importance among the factors (static and dynamic are both possible) that could potentially influence the stresses and earthquakes in the Philippine Sea plate.琉球隱沒帶震源機制解板塊內部應力中深層地震Ryukyu subduction zonefocal mechanisminternal stress of slabintermediate-depth earthquakes