Radar Scattering Characteristics and Stress Field of Lobate Scarps in the Apollo Basin on the Moon
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摘要: 月球叶状陡坎是月表浅层逆冲断层活动形成的小型线性构造,其空间分布与应力特征为揭示月球晚期构造演化提供了关键线索。目前,叶状陡坎的应力特征与雷达散射响应间的关联机制尚不明确。该研究以阿波罗盆地叶状陡坎为研究对象,利用Mini-RF影像提取散射特性参数;然后基于高分辨率数字高程模型采用库仑软件反演区域应力场分布特征;在此基础上,从统计关联角度分析雷达散射特征与应力之间的对应关系,揭示其构造活动性与表面物质响应的关联机制。主要结论如下:(1) 断层附近应变显著高于外围,最大剪应变集中于断层倾向方向,体应变显示断层上盘体积膨胀,两端及滑动面中心呈现体积收缩。(2) 陡坎面与上盘区域在圆极化比与部分极化分解参数上表现出更强的散射响应,表明这些区域可能存在更高的破碎度、块石暴露或结构复杂性,然而散射差异同时受到表面粗糙度、入射几何条件和后期改造过程的综合影响。(3)基于多元线性回归和随机森林算法进行了散射参数与应力场的回归分析,说明散射特征与应力之间的关联更可能是受地形条件、表面粗糙度及局部构造等共同作用的非线性关系。总体而言,该研究建立了一个面向阿波罗盆地叶状陡坎的雷达—地形联合探索性分析框架,用于评估散射特征与应力指标之间是否存在可量化的统计对应关系,并为相似地质背景下的浅层构造活动研究提供参考。Abstract: Lunar lobate scarps are small-scale linear structures formed by shallow thrust fault activity on the lunar surface, and their spatial distribution and stress characteristics provide essential clues for understanding the late-stage tectonic evolution of the Moon. At present, the correlation mechanism between the stress characteristics of lobate scarps and their radar scattering response remains unclear. In this study, lobate scarps in the Apollo Basin are considered as the research focus, and scattering characteristic parameters are extracted from Mini-RF images. Subsequently, the Coulomb software is used to invert the distribution characteristics of the regional stress field based on high-resolution digital elevation models. On this basis, the correspondence between radar scattering characteristics and stress is analyzed using statistical correlation methods, revealing the underlying relationship between tectonic activity and surface material response. The main conclusions are as follows. (1) The strain near the fault is markedly higher than that in the surrounding areas, with the maximum shear strain concentrated in the fault dip direction. Volumetric strain indicates volume expansion within the fault hanging wall, whereas volume contraction is observed at both ends and at the center of the sliding surface. (2) The scarp face and hanging wall regions exhibit stronger scattering responses in terms of the circular polarization ratio and partial polarization decomposition parameters, suggesting higher degrees of fragmentation, boulder exposure, or structural complexity in these areas. However, the scattering differences are also influenced by the combined effects of surface roughness, incidence geometry, and subsequent modification processes. (3) The regression analysis of scattering parameters and stress fields, based on multiple linear regression and random forest algorithms, indicates that the correlation between scattering characteristics and stress is likely nonlinear, governed by the combined effects of topographic conditions, surface roughness, and local structures. Overall, this study develops an exploratory radar-topography joint analysis framework for lobate scarps in the Apollo Basin to evaluate whether a quantifiable statistical correspondence exists between scattering features and stress indicators, as well as to provide supplementary evidence for studies of shallow tectonic activity under similar geological settings.
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表 1 研究区域叶状陡坎面散射特性的统计结果
Table 1. Statistical results of surface scattering characteristics of lobate scarps in the study area
陡坎 ID S0均值 CPR均值 m均值 χ均值 1 0.069 0.479 0.355 26.561 2 0.074 0.490 0.436 40.267 3 0.081 0.451 0.526 41.073 4 0.090 0.546 0.448 39.420 5 0.089 0.427 0.549 37.492 6 0.069 0.480 0.467 37.789 7 0.074 0.541 0.451 37.452 8 0.060 0.612 0.449 36.708 9 0.191 0.389 0.557 38.395 10 0.058 0.867 0.413 33.714 11 0.060 0.718 0.400 30.893 12 0.071 0.656 0.439 33.451 13 0.073 0.637 0.394 28.003 14 0.094 0.879 0.386 17.771 均值 0.083 0.583 0.448 34.213 表 2 研究区域叶状陡坎上盘和下盘散射特性的统计结果
Table 2. Statistical results of hanging wall and foot wall scattering characteristics of lobate scarps in the study area
陡坎 ID 部位 S0均值 CPR均值 m均值 χ均值 1 下盘 0.077 0.506 0.489 38.918 2 上盘 0.057 0.469 0.342 37.813 下盘 0.075 0.439 0.528 44.549 3 上盘 0.065 0.564 0.452 36.077 下盘 0.075 0.432 0.503 42.140 4 上盘 0.074 0.512 0.469 39.509 下盘 0.106 0.392 0.554 40.286 5 上盘 0.102 0.370 0.543 38.980 下盘 0.126 0.502 0.544 43.609 6 上盘 0.087 0.449 0.518 37.791 下盘 0.089 0.379 0.572 39.166 7 上盘 0.069 0.534 0.459 39.438 下盘 0.079 0.186 0.533 38.118 8 上盘 0.064 0.593 0.425 34.996 下盘 0.175 0.438 0.550 32.211 9 上盘 0.094 0.398 0.544 38.526 下盘 0.116 0.406 0.559 36.884 10 上盘 0.052 0.758 0.369 30.306 下盘 0.071 0.579 0.427 35.291 11 上盘 0.065 0.732 0.377 27.730 下盘 0.071 0.671 0.410 31.471 12 上盘 0.086 0.571 0.449 34.133 下盘 0.080 0.618 0.430 33.592 13 上盘 0.089 0.594 0.439 34.137 下盘 0.095 0.644 0.405 32.008 14 上盘 0.065 0.887 0.348 17.569 下盘 0.064 0.910 0.327 18.737 均值 上盘 0.073 0.572 0.441 34.385 下盘 0.090 0.507 0.488 36.212 表 3 研究区域叶状陡坎形态参数与库仑应力统计结果
Table 3. Statistical results of morphological parameters and Coulomb stress of lobate scarps in the study area
陡坎 ID 经度(°) 纬度(°) 长度(m) 深度(m) 起伏度(m) 库仑应力均值(MPa) 1 –160.877 –34.090 2266.73 804.68 13.33 0.383 2 –160.872 –34.094 685.12 222.56 7.69 1.308 3 –160.951 –34.142 866.58 296.90 13.57 0.755 4 –160.970 –34.204 5677.90 1892.46 18.81 0.270 5 –160.999 –34.298 563.50 183.68 7.56 –0.100 6 –161.007 –34.321 1970.36 645.48 7.98 –0.106 7 –161.013 –34.341 1300.02 440.93 8.41 0.073 8 –161.083 –34.395 672.92 219.58 7.64 0.001 9 –161.089 –34.659 1886.88 613.50 78.77 –0.241 10 –161.350 –34.789 652.72 220.84 13.86 0.093 11 –161.380 –34.830 1184.92 399.35 3.42 0.401 12 –161.425 –34.853 1715.37 596.13 28.13 0.570 13 –161.466 –34.890 1440.30 489.98 35.52 1.120 14 –161.622 –35.035 954.18 303.57 7.38 –0.202 表 4 对象内验证下模型性能对比
Table 4. Within-object validation model performance comparison
模型 多元线性回归 随机森林 MAE 0.231 0.136 RMSE 0.410 0.256 R2 0.569 0.832 Spearman ρ 0.809 0.916 表 5 5折GroupKFold交叉验证下模型泛化能力对比
Table 5. Model generalization performance comparison under 5-Fold groupkfold cross-validation
模型 多元线性回归 随机森林 各折测试集 R2范围 –0.715~–0.084 –0.776 ~–0.114 平均折间指标
(MAE/RMSE/R2)0.472/0.623/–0.427 0.486/0.635/–0.491 OOF总体指标
(MAE/RMSE/R2)0.464/0.665/0.132 0.478/0.674/0.165 表 6 Leave-One-Group-Out交叉验证下模型泛化能力对比
Table 6. Model generalization performance comparison under leave-one-group-out cross-validation
模型 多元线性回归 随机森林 MAE 0.467 0.474 RMSE 0.658 0.661 R2 –0.109 –0.120 表 7 剔除#9后对象内验证下模型性能对比
Table 7. Within-object validation model performance comparison after excluding #9
模型 多元线性回归 随机森林 MAE 0.235 0.139 RMSE 0.415 0.260 R2 0.568 0.831 表 9 剔除#9后Leave-One-Group-Out交叉验证下模型泛化能力对比
Table 9. Model generalization performance comparison under leave-one-group-out cross-validation after excluding #9
模型 多元线性回归 随机森林 MAE 0.475 0.481 RMSE 0.666 0.668 R2 -0.112 -0.117 表 8 剔除#9后5折GroupKFold交叉验证下模型泛化能力对比
Table 8. Model generalization performance comparison under 5-Fold groupkfold cross-validation after excluding #9
模型 多元线性回归 随机森林 平均折间指标 (MAE/RMSE/R2) 0.496/0.642/-0.503 0.510/0.653/-0.567 OOF总体指标 (MAE/RMSE/R2) 0.477/0.676/-0.143 0.491/0.685/-0.175 -
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