The cause of crustal deformation in the vicinity of Zhangbei earthquake area：Discussion with Wang Chao and Zhang Hong et al.

The paper with the ntle ot “The coseismic displacement field of the Zhangbei-Shangyi earthquake mapped by differential radar interfereometry” (“Displacement”for short hereinafter) published in Chinese Science Bulletin by Wang Chao et al. in Mar. 2000 introduced the coseismic uplift deformation in the vicinity of Zhangbei     

Discovery of a large area of ice-wedge networks in Ordos： Implications for the southern boundary of permafrost in the north of China as well as for the environment in the latest 20 kaBP

Deep sea deposits, ice cores and loess deposits have been used extensively and successfully, to study global climatic changes. Since permafrost is a consequence of cold climates, indicators of permafrost can also be used to reconstruct ancient climates in certain areas during certain periods. The recent discovery of large areas of ice wedge networks, and determination of their ages, have enabled us to locate the southern boundary of the permafrost that ex-isted in China about 20 thousand years…     

论《太平经》的词典学价值

分析《太平经》中的双音节词语,指出其所具的词典学价值,具体表现在增补失收词条、添补失收义项、提早书证年代、补充缺失书证四方面。     

Characteristics of the crustal structure and hypocentral tectonics in the epicentral area of Nan’ao earthquake (M7.5), the northeastern South China Sea

1918 Nan’ao earthquake (M7.5) occurred in the northeast coastal areas of Guangdong Province. With the seismogeological survey of the epicentral area and history materials analyses, the earthquake epicenter was estimated to locate in the intersection part of the Binhai fault zone (Littoral) and Huanggangshui fault, which strikes NEE and NW, respectively. The activities of the NEE-striking thrust fault and NW-striking extensional fault that were attributed to 1918 Nan’ao earthquake occurred in the Dongshan Island of the epicentral area; they reflected the focal stress field with compression in NW-SE direction and extension in NE-SW direction. The isoseismal contour of seismic intensity X shows a shape of ‘X’ composed of two mutually overlapping ellipses with two axes striking NEE and NW, respectively, and such shape implies that the occurrence of this earthquake is controlled by a pair of conjugate seismotectonic faults constituted by the NEE-striking Binhai fault zone and the NW-striking Huanggangshui fault. The Binhai fault zone is a dominant seismogenic structure, and the NW-striking Huanggangshui fault is the subdominant one. The onshoreoffshore deep seismic profile that crossed the epicentral area and was perpendicular to the strike of the Binhai fault zone was obtained. According to the analyses of the seismic data, the Binhai fault zone is defined as a low velocity zone with SE dip-slip in thecrustal structure section. The Binhai fault zone is a boundary fault between the South China subplate and South China Sea subplate. The crust structure on the northwest side of Binhai fault zone is a normal continental crust with a thickness of 30 km, and the one on the southeast side of the fault zone is a thinning continental crust with a thickness of 25―28 km. The Binhai fault zone is an important seismogenic fault and also is an earthquake-controlling fault. The intersection part between the Binhai fault zone and the low velocity zone of upper crust is advantageous to stress concentration and strain energy accumulation, and presents the deep dynamic conditions for the earthquake’s pregnancy and occurrence.     

鸟取MJMA 7.3级地震震源区地震层析成像研究

采用2000年日本鸟取MJMA7.3级地震的907个余震及其地方震的24 756个P波和22 547个S波到时,确定鸟取地震震源区的P波、S波和泊松比的三维结构.在震源区地震波速变化幅度达4%,泊松比变化幅度达9%.在11 km深度发现高波速和低泊松比异常,表明这一部位为刚性的粗糙断层面,形成断裂带的锁定结构,它的破裂产生鸟取地震的主震.低波速和高泊松比异常在震源区之下的地壳中出现,这与菲律宾板块俯冲带的脱水过程和岩浆活动有关,导致Daisen弧后火山的形成.流体运动和岩浆活动,对鸟取地震的成核和破裂过程有重大的影响.     

Significant isostatic imbalance near the seismic gap between the M8.0 Wenchuan and M7.0 Lushan earthquakes

A gravity network with 302 observation points has been established in the western Sichuan Foreland Basin （SFB） to explore Bouguer gravity anomalies （BGAs）. Our observational results reveal that the BGAs are negative as a whole, with a maximum value of -220 mGal （10^-5m s^-2） at the northwest region of the study area. The real Moho depths beneath the SFB revealed by BGA data change smoothly from 39.5 km in the southeast to 43.7 km in the northwest of the monitoring region. However, the isostatic ones deduced from Airy isostatic model and topographical data vary approximately 39.5-42.0 km. The maximum differences of 2.7 km between the real and isostatic Moho depths are found near the seismic gap between the M8.0 Wenchuan and M7.0 Lushan earthquakes, where the crust is in the greatest isostatic imbalance of the monitoring region. Analysis of the isostatic state indicates that the deep dynamic environment near the seismic gap between these two earthquakes indicates an M ≥ 7.0 earthquake in the future. This study indicates that we can use isostasy as a potential approach to study the dynamic process of crustal material movement and to analyze regional potential seismic risks.     

北京地区新构造运动特征与地震的关系

北京地区是新构造运动表现明显地区之一.新第三纪以来受地应力作用,发生各种地壳形变,它直接表现在构造演化和地貌形态上.这种活动与本区地震有着密切的关系.     

近场竖向地震动对铁路桥梁地震反应的影响

采用非线性三维空间梁单元来建立桥墩的有限元模型,选用了三组不同类型的地震记录作为输入,研究近场竖向地震动对我国目前常用的钢筋混凝土铁路简支梁桥桥墩地震反应的影响。研究结果表明,在最大峰值水平加速度PGA分别为0．1g和0．2g的地震输入下,桥墩结构均处于弹性工作状态,相应的竖向地震动对桥墩的地震反应影响很小（均不超过2％）;而在最大峰值水平加速度PGA为0．4g的地震输入下,桥墩显示了非线性行为,竖向地震动对桥墩地震反应的影响显著增大,尤其是因P—A效应的影响会使桥墩的墩顶位移显著增加。     

下地幔可以发生地震吗?

大部分的地震发生在比较浅的位置,但是部分地震的深度可以达到600 km以上.目前已有的破裂机制预测地震只存在于上地幔中,但是一些地震的初步定位深度却可以超过670 km(1998年2月9号Okhotsk海地震,地震目录中被定为678 km).研究表明大多数浅震是由于断层失稳,沿着已有的断层面突然滑动引发的,而深震的发震机制目前尚无定论,尤其是下地幔中是否发生地震对于研究深震机制可以提供重要的约束.因为地球中的横向不均匀性,地震的绝对深度有较大的误差,所以我们根据观测地震图中明显的三重值特征,对上述那次深地震进行波形模拟,把相对深度和绝对深度结合起来,最终确定地震实际发生在670公里间断面以上,因此我们认为目前目录中那些最深的地震仍然发生在上地幔中.     

平顶山市2.5级地震调查研究

调查研究了平顶山市2003年2.5级地震,进而分析了平顶山市地震趋势;对平顶山市的建设发展具有重要的参考价值.     

广西靖西Ms5.2级地震基本情况与灾害特征分析

2019年11月25日广西靖西市湖润镇发生M_s5.2级地震,该地震震情特征在同级地震中具有很好的代表性,是研究解剖中强地震的典型震例。本文介绍了广西靖西M_s5.2级地震的地震序列,分析此次地震的余震特征,总结此次地震震区的地质构造和地形地貌特点。通过对震区开展房屋结构、房屋震害、地震次生地质灾害等调查,评定地震烈度及灾害损失。分析表明,广西靖西M_s5.2级地震为主余震型地震,余震强度大,分布集中。此次地震烈度Ⅵ度区虽面积不大,但震害较严重。此外,分析还表明地质地貌条件和抗震设防的差异会造成较大的震害差异。