山地城镇发展受限于地形地貌，出现了以新城建设为主的城市扩张模式。该模式地理空间 表现为新城建设远离主城区，城市建设用地逐渐向更高的坡度上扩张（即建设用地梯度扩张）。梯 度扩张虽解决山地城镇土地资源紧缺问题但也提高了诸如地面沉降等地质灾害的风险，探究梯度扩 张规律以及识别灾害风险为重中之重。研究选取梯度扩张程度剧烈的3 个新城作为典型案例区域， 利用数字高程模型获取了2017—2022 年新区梯度扩张区域，基于2016—2020 年Sentinel-1A SAR 数据利用SBAS-InSAR 技术得到地表形变信息，揭示新区梯度扩张与地面沉降之间的空间关联。 结果表明：①2017—2022 年，延安新区、两江新区和兰州新区的梯度扩张现象显著，梯度扩张区占 比分别为53.5%、51.0% 和45.2%，受地形影响最严重的延安新区梯度扩张区占比最高，梯度扩张速 度与城市扩张速度趋势基本相符。②延安新区、两江新区和兰州新区最大沉降速分别为28 mm/a、 30 mm/a 和29 mm/a，沉降多发生在新区扩张前沿且沉降区周围均存在不同规模梯度扩张区域。 ③梯度扩张强度与地面沉降速率为正相关，高梯度扩张强度和高地面沉降速率区域的集聚分布表 示城市梯度扩张加速了扩张区地面沉降的发生。研究对探究城市梯度扩张与地面沉降关联，推动 山地城市可持续发展有着积极的意义。

The development of mountainous towns is limited by terrain and landforms, resulting in an urban expansion model dominated by new city construction. The geographical spatial manifestation of this model is that the construction of new cities is far from the main urban area, and the urban construction land gradually expands towards higher slopes (i.e., the gradient expansion of construction land). Although gradient expansion solves the problem of land resource scarcity in mountainous towns, it also increases the risk of geological disasters such as land subsidence. Exploring the law of gradient expansion and identifying disaster risks are paramount. The study selected three new cities with severe gradient expansion as typical case areas and used DEM to obtain the gradient expansion areas of the new areas from 2017 to 2022. Based on Sentinel-1A SAR data from 2016 to 2020, SBAS InSAR technology was used to obtain surface deformation information, revealing the spatial correlation between gradient expansion and land subsidence in the new areas. ① The results show that from 2017 to 2022, the gradient expansion phenomenon in Yan’an New Area, Liangjiang New Area, and Lanzhou New Area was significant, with gradient expansion areas accounting for 53.5%, 51.0%, and 45.2%, respectively. Yan'an New Area, which is most severely affected by terrain, has the highest proportion of gradient expansion areas, and the gradient expansion speed is consistent with the urban expansion speed trend. ② The maximum settlement velocities in Yan’an New Area, Liangjiang New Area, and Lanzhou New Area are 28mm/a, 30mm/a, and 29 mm/a, respectively. Settlement mostly occurs at the front of the expansion of the new area, and there are different scale gradient expansion areas around the settlement area. ③ The intensity of gradient expansion is positively correlated with the rate of land subsidence, and the clustering distribution of areas with high gradient expansion intensity and high ground subsidence rate indicates that urban gradient expansion accelerates the occurrence of land subsidence in the expansion area. The study has positive significance in exploring the correlation between urban gradient expansion and land subsidence and promoting sustainable development of mountainous cities.