黑龙江五大连池火山群的地貌形态和分形特征及其成因

Topography and Fractal Characteristics and Their Genesis of the Wudalianchi Volcanic Group in Heilongjiang

火山地貌及其成因研究对深入揭示火山形成与行星表面形态演化具有重要意义。本文基于黑龙江五大连池火山区的遥感影像和数字高程模型(DEM)数据,对火山群形貌进行综合解译和地貌分形分析,从系统科学角度讨论形成本区火山地貌系统的复杂成因机制。研究结果表明:(1)火山锥和熔岩地貌构成了区内低起伏频率的地表形态,断裂带上复合型火山锥的分布数量影响该方向上的地形复杂度。(2)火山群地貌分形具有多度域分形结构且分形维数较小(D≈2),推测是受到大面积熔岩地貌和低矮火山锥影响造成的。沿断裂构造方向的地形剖面分形维数显示,五大连池地区三组断裂方向的地貌各向异性较小(D值为1.142~1.275,D_(max)与D_(min)仅相差0.133),NE方向的分形维数较大(D_(NE)为1.223~1.275),是影响火山群地貌形成的主要断裂方向。(3)火山群地貌特征受到内外营力协同控制,深浅两套断裂构造和岩浆系统是影响现阶段火山区形貌的主要因素。外营力在中微观尺度随机粗化作用正在加强,但在宏观尺度上尚未占协同对抗上风,区域形态还未发生改变。遥感波谱特性与地貌形态分析对火山地貌研究是有效的,地貌分形分析可以量化不同尺度下的地貌形态特征,这为火山区地貌及其成因机制研究提供了新的思路和方法。

Volcanic topography is essential to study the formation of volcanoes and evolution of planetary morphology.Based on the remote sensing images and DEM data of the Wudalianchi volcanic area,we analyzed fractal characteristics and performed the comprehensive interpretation in its formation,and discussed the complex genetic mechanisms of the geomorphic system in this volcanic area.The results show that(1)volcanic cones and lava topography constitute the surface morphology with low undulation frequency in the area,and the number of composite volcanic cones distributed along the fractures affects the topographic complexity in this direction.(2)The topography of this area shows a fractal structure of multiscale domains and a small fractal dimension(D≈2),which was presumably influenced by the extensive lava topography and low volcanic cones.The fractal dimensions of the topographic profiles in the directions of fractures show that the geomorphic anisotropy of the three fracture directions in the Wudalianchi volcanic area is relatively small(D=1.142-1.275),and the difference between D_(max) and D_(min) is only 0.133.However,the fractal dimensions in the NE direction are large(D_(NE)=1.223-1.275),which is the principal fracture direction affecting the volcanic topography.(3)The topographic characteristics of the volcanic group are determined by internal and external agents,and two sets of fractural structures(deep and shallow fractures)and magmatic systems are the main factors affecting its topographic features at the present stage.The role of external agent in stochastic coarsening at the meso-to-micro scale is intensifying,but synergistic antagonism has not yet prevailed at the macro scale,and the complex regional topography of the volcanic group has not yet changed.Remote sensing spectral features and topographic analyses are effective to investigate the volcanic topography,and the quantitative fractal characteristics can interpret the topographic characteristics at different scales and becoming a novel approach to study volcanic topography and their genesis.