2023年積石山MS6.2地震發震斷層傾向爭議討論與相鄰斷裂地震危險性評估

摘要： 2023年12月18日甘肅省積石山縣發生MS6.2地震。選取Sentine1-1A升、降軌SAR衛星影像，采用差分合成孔徑雷達干涉測量（D-InSAR）技術獲取此次地震的同震形變場。結果顯示，升、降軌LOS向同震形變場長軸為NW—SE向，變形為正值，向衛星方向靠近，揭示出地表抬升，升、降軌LOS向最大形變量分別為12 cm和9 cm。以升、降軌形變數據為約束，采用梯度下降法（SDM）反演同震滑動分布。反演結果表明：發震斷裂西南傾向和東北傾向斷層模型均能較好地正擬合合成孔徑雷達干涉測量（InSAR）同震形變場觀測值，反映出積石山地震為逆沖兼走滑型。為解決此次地震發震斷層及傾向爭議，重點結合區域構造背景和余震分布，推測其發震斷層為一條走向NW—SE且傾向SW的隱伏斷層，走向～148.4°，傾角52°，滑動角～130°，可能為積石山東緣斷裂分支斷層。同震庫侖應力模型顯示，臨潭—宕昌斷裂東段、冷龍嶺斷裂東段、海原斷裂西段、拉脊山南緣斷裂西段、貴德斷裂等斷層段位于同震庫侖應力變化（ΔCFS）正、負跨界轉換處，應給予關注。

關鍵詞： InSAR; 積石山MS6.2地震; 同震形變場; SDM; 斷層滑動分布

中圖分類號： P315""""" 文獻標志碼：A"" 文章編號： 1000-0844（2025）02-0480-12

DOI：10.20000/j.1000-0844.20240520001

Discussion on the controversies of seismogenic fault dipping direction

for 2023 Jishishan MS6.2 earthquake and seismic

hazard assessment of its adjacent faults

PING Zifei1， GE Weipeng^1，2， ZHANG Bo1， ZHU Junwen1， CAO Xiyu1

（1.Lanzhou Institute of Seismology，CEA，Lanzhou 730000，Gansu，China;

2.Gansu Lanzhou Geophysics National Observation and Research Station， Lanzhou 730000， Gansu， China）

Abstract：

On December 18， 2023， an MS6.2 earthquake occurred in Jishishan County， Gansu Province. The ascending and descending Sentinel-1A SAR satellite images were selected and the differential interferometric synthetic aperture radar （D-InSAR） technology was used to obtain the co-seismic deformation field of the earthquake. The results show that the long axis direction of co-seismic deformation field in the line of sight （LOS） direction is NW-SE， and the deformation is positive， indicating an approach towards the satellite and revealing surface uplift. The maximum deformation in the LOS direction of ascending and descending tracks is 12 and 9 cm， respectively. Subsequently， the co-seismic slip distribution was inverted using the steepest descent method with ascending and descending deformation data as constraints. The inversion results show that both the SW-dipping and NE-dipping fault models fit the observed values of InSAR co-seismic deformation field well， indicating that the MS6.2 earthquake is a combined thrust/strike-slip faulting type. The tectonic background and aftershock distribution in the study area were discussed to solve the controversies on the seismogenic fault and its dipping direction of the event. It is inferred that the seismogenic fault of the Jishishan MS6.2 earthquake is a hidden fault striking NW-SE and dipping SW， with a strike of approximately 148.4°， a dip angle of 52°， and a slip angle of approximately 130°， possibly a branch fault of the Jishishan east margin fault. Additionally， the co-seismic Coulomb stress model shows that the eastern section of Lintan-Tanchang fault， the eastern section of Lenglongling fault， the western section of Haiyuan fault， the western section of Lajishan southern margin fault， and the Guide fault are located at the positive-negative transition zone of co-seismic Coulomb failure stress change （ΔCFS）， which should be given attention.

Keywords：

InSAR; Jishishan MS6.2 earthquake; co-seismic deformation field; SDM; fault slip distribution

0 引言

據中國地震臺網測定（https：//news.ceic.ac.cn/），北京時間2023年12月18日23時59分，甘肅省臨夏州積石山縣發生MS6.2地震，震源深度10 km，震區最大烈度為Ⅷ度。此次地震震中位于甘肅省臨夏回族自治州積石山縣柳溝鄉（102.79°E，35.7°N）。截至2023年12月24日6時，共記錄到余震538次，其中3.0級及以上余震11次，最大余震4.1級，均位于主震北部，且呈北西向分布。積石山地震發生后，國內外不同機構及學者采用不同的方法獲得了該地震的震源機制解（表1），一致認為其是一次逆沖型地震。……