基于InSAR技术的甘肃积石山震区活动滑坡识别与动态形变监测

2023-12-18,甘肃省临夏回族自治州积石山县发生Ms 6.2地震,造成150余人遇难及大量建筑物倒塌,并诱发了同震滑坡灾害。此外,地震还将加速活动滑坡的形变,严重威胁人民生命财产和基础设施的安全,亟需开展震区活动滑坡快速识别与动态形变监测研究。基于此,提出了一种基于合成孔径雷达干涉测量（interferometric synthetic aperture radar,InSAR)技术的地震区活动滑坡自动化识别与动态形变监测框架。采用2017年3月至2023年12月的升轨与降轨Sentinel-1影像,反演获得InSAR相位梯度速率、年平均形变速率及时间序列,建立了DeepLabv3深度学习滑坡自动化识别方法,快速绘制研究区域的活动滑坡编目图,并开展滑坡空间分布特征研究;并采用序贯InSAR技术实现了新获得的合成孔径雷达影像的快速处理,进行滑坡形变的动态监测,及时捕获地震造成的滑坡形变加速信号。研究结果表明,在积石山震中70 km范围内分布有2 021个不同尺度的潜在活动滑坡,集中在6个高密度分布区,主要分布在距断层22 km、距河流28 km、距道路10 km范围内和高程3 400 m以下、坡度为15°~35°的区域,且主要沿着正北向、东北及正东向分布;本次地震造成积石山县及黄河沿线部分区域的滑坡形变出现显著加速,降低了斜坡的稳定性,现场调查验证了动态形变监测结果的可靠性。所提方法可为类似地震事件的活动滑坡快速调查及动态监测提供重要技术指导,研究成果可为震后灾区重建及次生滑坡灾害风险评估提供科学数据支撑。     

基于高频GNSS观测的甘肃积石山Ms 6.2地震同震形变

2023-12-18发生的甘肃积石山6.2级地震造成了重大的人员伤亡。收集了不同系统32个卫星导航定位基准站（continuously operating reference stations,CORS）当天的高频全球导航卫星系统（global navigation satellite system,GNSS）观测数据,进行了高精度动态单历元数据处理。结果发现,震中附近50 km以内的高频GNSS可以监测到明显的同震形变波形,峰值变化最大达到50~60 mm;地震永久变形主要影响范围为距离震中30 km的区域,距离震中5 km的测站记录到东西向永久变形~13 mm、南北向变形~10 mm,以及~8 mm的垂向变形。采用自适应噪声完全集合经验模态分解方法对高频GNSS波形信号进行分解,可分离出明显的同震形变信号,最远可探测到距离震中100 km。采用模态分解方法可探测出更多的同震信号,这为利用丰富的CORS资源监测地震的同震形变提供更多可行性。     

Data augmentation for bias correction in mapping PM2.5 based on satellite retrievals and ground observations

As most air quality monitoring sites are in urban areas worldwide,machine learning models may produce substantial estimation bias in rural areas when deriving spatiotemporal distributions of air pollutants.The bias stems from the issue of dataset shift,as the density distributions of predictor variables differ greatly between urban and rural areas.We propose a data-augmentation approach based on the multiple imputation by chained equations(MICE-DA)to remedy the dataset shift problem.Compared with the benchmark models,MICE-DA exhibits superior predictive performance in deriving the spatiotemporal distributions of hourly PM2.5 in the megacity(Chengdu)at the foot of the Tibetan Plateau,especially for correcting the estimation bias,with the mean bias decreasing from-3.4 μg/m3 to-1.6 μg/m3.As a complement to the holdout validation,the semi-variance results show that MICE-DA decently preserves the spatial autocorrelation pattern of PM2.5 over the study area.The essence of MICE-DA is strengthening the correlation between PM2.5 and aerosol optical depth(AOD)during the data augmentation.Consequently,the importance of AOD is largely enhanced for predicting PM2.5,and the summed relative importance value of the two satellite-retrieved AOD variables increases from 5.5％to 18.4％.This study resolved the puzzle that AOD exhibited relatively lower importance in local or regional studies.The results of this study can advance the utilization of satellite remote sensing in modeling air quality while drawing more attention to the common dataset shift problem in data-driven environmental research.     

The Middle Miocene lobe-shaped and band-shaped submarine fans in the Lingshui Sag,Qiongdongnan Basin: source-to-sink system,genesis and implication

Deepwater oil and gas exploration is the key to sustainable breakthroughs in petroleum exploration worldwide.The Central Canyon gas field has confirmed the Lingshui Sag is a hydrocarbon-generating sag, and the deepwater reservoirs in the Lingshui Sag still have more fabulous oil and gas exploration potential. Based on drilling data and three-dimensional(3D) seismic data, this paper uses seismic facies analysis, seismic attribute analysis, and coherence slice analysis to identify the types of submarine fans(lobe-shaped and band-shaped submarine fans)that developed in the Lingshui Sag during the Middle Miocene, clarify the source-to-sink system of the submarine fans and discuss the genesis mechanism of the submarine fans. The results show that:(1) the deepwater source-to-sink system of the Lingshui Sag in the Middle Miocene mainly consisted of a “delta(sediment supply)-submarine canyon(sediment transport channel)-submarine fan(deepwater sediment sink)” association;(2) the main factor controlling the formation of the submarine fans developed in the Lingshui Sag was on the relative sea level decline; and(3) the bottom current reworked the lobe-shaped submarine fan that developed in the northern Lingshui Sag and formed the band-shaped submarine fan with a greater sand thickness. This paper aims to provide practical geological knowledge for subsequent petroleum exploration and development in the deepwater area of the Qiongdongnan Basin through a detailed analysis of the Middle Miocene submarine fan sedimentary system developed in the Lingshui Sag.     

渤海海域印支期构造变形分带性及其特征的数值模拟研究

印支运动为现今渤海海域构造格局的形成奠定了基础,导致渤海海域内部发育3个主要逆冲带。渤海基底内部的先存断层与滑脱层在此过程中可能起到了极为重要的作用,但其如何影响渤海海域印支期的构造变形与分带特征的机制尚不清楚。为了解决上述问题,本文基于地震剖面数据,结合二维热力学数值模拟代码LaMEM对渤海海域印支期的构造变形展开了详细研究。模拟结果揭示,在先存断层存在的条件下,当基底内部无滑脱层或未呈阶梯式在渤海海域分布时,渤海海域内部不会形成相应的逆冲中心;而当基底内部的滑脱层呈阶梯状分布在渤海海域西南部、渤中坳陷以及辽东坳陷3个区域时,应力通过滑脱层在基底内部进行传导,使海域形成了3个逆冲中心,并导致渤海内部大规模的逆冲断层与褶皱变形的发育,与地震剖面具有较好的一致性。数值模拟实验结果证实,基底内部的先存断层与滑脱层是控制渤海海域构造分带性及构造变形特征的重要因素。同时,多逆冲中心演化模式也为解释现今龙门山和四川盆地的形成与演化过程提供了重要的借鉴。     

滨里海盆地早二叠世孔谷期盐构造特征及其形成机制

滨里海盆地为自寒武系以来多期沉降的大型叠合含盐盆地,也是世界上油气资源最丰富的大型沉积盆地之一。下二叠统孔谷阶含盐层系在全盆皆有分布,岩盐层具有厚度大、分布广、后期变形构造样式多等特征,但厚层岩盐形成机制尚有争议,盐构造变形类型、空间组合分布规律、变形主控因素等尚不明确。为了研究盆地巨厚盐构造的形成机制及分布规律,在深入了解区域地质背景基础上,利用二维地震剖面资料,采用平衡剖面恢复方法,从全盆地的角度分析盆地演化过程与盐构造变形样式及分布规律,并探讨了盆地盐构造形成演化过程及触发机制。结果表明,盐岩变形程度由盆地中央向盆地边缘减小,由盆缘盐滚、盐背斜构造向盆地中心盐墙构造变化,呈现分带特征。盐岩层的变形对盐下地层影响较小,地层连续性较好;对盐上地层穿插切割较强,导致盐上地层连续性差,形变剧烈。先存斜坡和盆缘的挤压作用是盐岩层最初开始形变的因素,而上覆地层的差异负载作用是盐岩层发生构造变形的主导因素。滨里海盆地连续且巨厚的致密盐岩层是一个天然盖层,阻止了油气向上运移,盐下地层应是未来油气勘探的重点目标,同时,局部岩盐变形消失后使上下地层连接,利于油气向上运移成藏,形成盐上油气勘探目标区。