索羅門群島位於太平洋西南邊緣，介於太平洋板塊與澳洲板塊之間，是一個構造極為複雜的區域。由於地震活動頻繁，該地區在過去幾十年間曾發生多次大地震，突顯出取得詳細的地震與地球科學相關資料的重要性。本研究聚焦於索羅門群島東南部的南索羅門隱沒帶，分析兩起中等規模地震（MW 6.3 與 6.0）於2020年1月27日與29日發生的前震–餘震序列，更深入了解該區域的地震特性。整個前震–餘震序列皆由新建立的區域地震監測網所記錄，該監測網由紐西蘭地質與核子科學有限公司（GNS）部署，自2018年10月起開始運作。大多數的地震震央集中於Makira與Guadalcanal之間，形成一個向北傾、近乎垂直的地震群，震源深度從近地表延伸至約120公里。我們認為這個以逆衝斷層為主的地震群提供了南索羅門隱沒板塊與Makira-Santa Cruz轉形斷層相交且終止的證據。此外，我們也在地震群中25至50公里深度間發現一個地震空區。 透過模板匹配法，我們辨識出193個未被記錄在地震目錄的重複或近似重複地震事件，進一步提升了地震目錄的完整性。此方法在未來亦可用來辨識那些肉眼難以察覺的重複地震事件。另外，模板與檢測結果的統計關係也有助於顯示區域內的構造特徵與各測站的訊號品質。我們的研究中，NGOA測站展現出優異的表現，顯示出不同測站在穩定度與訊號捕捉效率上存在差異，這些結果為未來地震測站的佈設提供了寶貴的參考。 為了進一步評估地震波傳播與震源特性，我們進行了高頻震波分析與震源參數反演。觀測顯示，淺源與深源事件在波形特徵上有顯著差異，特別是前弧測站 NGOA 所記錄到的高頻能量（4-7 Hz）放大現象，定義了隱沒帶在 50-60 公里深處存在一個關鍵的邊界。透過頻譜擬合有效解耦路徑衰減(Q)與震源效應後，我們證實這些顯著的高頻訊號主要受控於隱沒板塊內的高效率傳播路徑，而非異常的高應力震源。另外，隨深度變化的應力降分析顯示出複雜的演化趨勢：應力降在 50-60 公里邊界處首先呈現下降，隨後在 60-70 公里處短暫回升，並在大於70 公里之深部區域再次下降。結合地震空區的觀測，這些變異提供了澳洲板塊在隱沒過程中力學相變的強力證據，涵蓋了中層深度的脫水與蛇紋岩化到深層區域的榴輝岩化或二次脫水作用。本研究結合高頻波形觀測與精確的反演分析，成功捕捉了南索羅門隱沒系統中流體驅動的流變學變化與複雜的震波傳播動力學。總結來說，本研究綜合地震分布、高頻波形觀測與精確的Q 值及震源參數反演，提出了一個南索羅門隱沒帶的概念構造模型。;The Solomon Islands is a tectonically complex region situated on the southwestern margin of the Pacific， between the Pacific and Australian plates. As a region with a high seismic rate， the Solomon Islands have experienced several large earthquakes over the past few decades， underscoring the importance of obtaining detailed seismological and geoscientific data in the area. In this study， we focused on the South Solomon subduction zone in the southeastern Solomon Islands and analyzed the foreshock-aftershock sequence of two moderate earthquakes (MW 6.3 and 6.0) that occurred on January 27th and 29th， 2020， to better understand the seismic characteristics of the region. The entire foreshock-aftershock sequence was recorded by a new regional seismic network， deployed by the Geological and Nuclear Sciences Limited (GNS)， New Zealand， which has been operational since October 2018. The majority of hypocenters form a steeply dipping earthquake cluster between Makira and Guadalcanal， deepening northward from near the surface to ~120 km in depth. We suggest that this thrust-dominated cluster provides evidence for the termination of the South Solomon subducting slab against the strike-slip M-SCT. In addition， we also identified a seismic gap within the event cluster at depths between 25 and 50 km. Using a template matching approach， we identified 193 previously undetected repeating or near-repeating earthquakes， improving the completeness of the seismic catalog. The method can help identify repeating or near-repeating earthquakes in the future that might be overlooked through visual inspection alone. Statistical patterns between templates and detections can reveal underlying structural features of the region as well as the signal quality of individual stations. Station NGOA exhibited superior performance， suggesting potential variations in station reliability and signal capture efficiency. These findings provide valuable insights for optimizing future seismic station deployments. To assess wave propagation and source characteristics， we conducted high-frequency seismic wave analysis and attenuation factor inversion. Distinct waveform differences between shallow and deeper events， particularly the amplified high frequencies (4–7 Hz) at forearc station NGOA， identify a major boundary at 50-60 km depth. By employing a robust two-step spectral fitting approach to decouple path attenuation (Q) from source effects， we demonstrate that these prominent high-frequency signals are primarily governed by highly efficient propagation paths within the subducting slab rather than anomalously high-stress sources. Our depth-dependent stress drop analysis reveals that this boundary marks a critical transition in source properties: stress drops initially exhibit a reduction at 50-60 km， followed by a transient recovery at 60-70 km， and a subsequent decreasing trend for deeper events (>70 km). Combined with the observed seismic gap (25-50 km)， these variations provide strong evidence for the transitions of the subducting Australian slab， ranging from dehydration and serpentinization at intermediate depths to eclogitization or secondary dehydration in the deeper regime. By integrating seismic data， high-frequency observations with precise Q and source parameter inversions， this study captures the complex interplay between wave propagation dynamics and the rheological evolution of the South Solomon subduction system. Synthesizing these seismic data， high-frequency observations with precise Q and source parameter inversions， we propose a comprehensive conceptual model of the South Solomon subduction system.
