逆时偏移中的归一化加权互相关成像条件及应用

成像条件是决定声波方程叠前逆时深度偏移效果的重要因素。常规的归一化互相关成像条件能补偿深部地层的反射波能量,但无法压制地震波逆时偏移过程中产生的偏移噪声。针对归一化互相关成像条件的主要缺陷,从二维声波方程出发,在交错网格空间中推导了声波方程逆时延拓的高阶有限差分格式和PML吸收边界条件,进而在对常规互相关成像条件分析的基础上对其进行改进,给出了一种加权互相关成像条件,即在成像过程中利用炮检波场的夹角进行加权校正,以实现只利用炮点下行波场与接收点上行波场进行成像的目标。模型数据和实测资料偏移结果表明,归一化加权互相关成像条件成像效果明显优于常规归一化互相关成像条件。     

华北板块南缘北东地区构造特征及矿井瓦斯主控因素

通过华北板块南缘北东地区的弧形构造特征、形成时代和瓦斯分布特征的研究,得出如下结论:1徐宿弧形构造限于丰沛断裂与蚌埠隆起北缘的五河断裂间,为形成于早三叠世后、晚侏罗世前的推覆构造;其形成与动力来源可能是扬子板块沿着郯庐断裂带向西或北西方向俯冲于华北板块之下的碰撞拼贴作用。2徐宿弧形推覆构造中和面外侧引张、内侧挤压的构造应力场是导致位于弧形内侧的宿东向斜内煤矿瓦斯富集、外侧闸河向斜瓦斯含量相对较少的主因之一;煤矿区内岩浆岩体(脉)的侵入改变了这种本应规律的瓦斯分布图案。岩浆活动和构造作用共同构建了华北板块南缘北东地区的构造和瓦斯分布图案。     

自然伽马拟声波曲线构建技术探讨

声波测井曲线在地震反演中起着约束和控制模型反演的作用,当其不能反映地层岩性变化时,通常会将现有的非声波测井曲线按照一定的经验公式或统计方法来重构新的声波曲线。但是,这些拟声波曲线构建技术并没有考虑到地层岩石孔隙及孔隙中流体的影响。在考虑到岩石孔隙和孔隙中流体的情况下,拟声波曲线构建技术可以先利用岩石基质的声波速度与自然伽马之间的关系来重构具有声波量纲的新曲线,然后结合原声波曲线中能够反映背景速度的低频信息,构建出新的声波曲线。该方法在鄂尔多斯盆地镇泾地区取得了不错的应用效果。     

新疆东准噶尔卡拉麦里蛇绿岩带研究现状

新疆东准噶尔卡拉麦里蛇绿岩带是一条重要的蛇绿岩带,其所代表的古大洋是中亚古生代构造框架中一个非常重要的构造单元。对于该带归属何古板块之间的缝合带存在着截然不同的认识,对卡拉麦里蛇绿岩前身洋盆俯冲闭合年限也存在多种观点。根据对前人研究资料的综合,简要地论述了该断裂带是准噶尔洋俯冲消亡的遗迹,其闭合年限在350Ma左右。     

Deep incision in an Aptian carbonate succession indicates major sea‐level fall in the Cretaceous

Long‐term relative sea‐level cycles (0·5 to 6 Myr) have yet to be fully understood for the Cretaceous. During the Aptian, in the northern Maestrat Basin (Eastern Iberian Peninsula), fault‐controlled subsidence created depositional space, but eustasy governed changes in depositional trends. Relative sea‐level history was reconstructed by sequence stratigraphic analysis. Two forced regressive stages of relative sea‐level were recognized within three depositional sequences. The first stage is late Early Aptian age (intra Dufrenoyia furcata Zone) and is characterized by foreshore to upper shoreface sedimentary wedges, which occur detached from a highstand carbonate platform, and were deposited above basin marls. The amplitude of relative sea‐level drop was in the order of tens of metres, with a duration of <1 Myr. The second stage of relative sea‐level fall occurred within the Late Aptian and is recorded by an incised valley that, when restored to its pre‐contractional attitude, was >2 km wide and cut ≥115 m down into the underlying Aptian succession. With the subsequent transgression, the incision was backfilled with peritidal to shallow subtidal deposits. The changes in depositional trends, lithofacies evolution and geometric relation of the stratigraphic units characterized are similar to those observed in coeval rocks within the Maestrat Basin, as well as in other correlative basins elsewhere. The pace and magnitude of the two relative sea‐level drops identified fall within the glacio‐eustatic domain. In the Maestrat Basin, terrestrial palynological studies provide evidence that the late Early and Late Aptian climate was cooler than the earliest part of the Early Aptian and the Albian Stage, which were characterized by warmer environmental conditions. The outcrops documented here are significant because they preserve the results of Aptian long‐term sea‐level trends that are often only recognizable on larger scales (i.e. seismic), such as for the Arabian Plate.     

Petrogenesis of the Yangchang Mo‐bearing granite in the Xilamulun metallogenic belt,NE China: geochemistry,zircon U–Pb ages and Sr–Nd–Pb isotopes

The Yangchang granite‐hosted Mo deposit is typical of the Xilamulun metallogenic belt, which is one of the important Mo–Pb–Zn–Ag producers in China. A combination of major and trace element, Sr, Nd and Pb isotope, and zircon U–Pb age data are reported for the Yangchang batholith to constrain its petrogenesis and Mo mineralization. Zircon LA‐ICPMS U–Pb dating yields mean ages of 138 ± 2 and 132 ± 2 Ma for monzogranite and granite porphyry, respectively. The monzogranites and granite porphyries are calc‐alkaline with K₂O/Na₂O ratios of 0.75–0.92 and 1.75–4.42, respectively. They are all enriched in large‐ion lithophile elements (LILEs) and depleted in high‐field‐strength elements (HFSEs) with negative Nb and Ta anomalies in primitive‐mantle‐normalized trace element diagrams. The monzogranites have relatively high Sr (380–499 ppm) and Y (14–18 ppm) concentrations, and the granite porphyries have lower Sr (31–71 ppm) and Y (5–11 ppm) concentrations than those of monzogranites. The monzogranites and granite porphyries have relatively low initial Sr isotope ratios of 0.704573–0.705627 and 0.704281, respectively, and similar ²⁰⁶Pb/²⁰⁴Pb ratios of 18.75–18.98 and 18.48–18.71, respectively. In contrast, the ε_Nd(t) value (−3.7) of granite porphyry is lower than those of monzogranites (−1.5 to −2.7) with Nd model ages of about 1.0 Ga. These geochemical features suggest that the monzogranite and granite porphyries were derived from juvenile crustal rocks related to subduction of the Paleo‐Pacific plate under east China. Copyright © 2013 John Wiley & Sons, Ltd.     

空间集聚对在京日企就业规模的影响研究

FDI企业的空间集聚已经成为重要空间现象,但其对FDI企业规模的影响尚未引起学者的重视。既有研究发现的国家尺度集聚对制造业企业规模扩张的促进效应,是否适用于制造业和服务业共存的大都市区尺度?这也需要进行再商榷。论文基于企业内部生产技术条件、企业外部交易行为,搭建了大都市区范围内企业规模分异的解析框架,利用在京日企微观数据,分析了其空间集聚特征,讨论了其就业规模与分工的时空间变动特征,解析了集聚对在京日企的就业规模影响。研究发现：① 在京日企围绕集聚中心,呈现清晰的中心-外围分异特征。1995—2016年,集聚程度增强,集聚区重心外移,集聚空间规模扩大。2016年时形成了使馆区-CBD集聚区、BDA亦庄集聚区、首都机场集聚区、Z-Park中关村集聚区。② 在京日企的单环节化、服务化空间分异特征明显。单环节日企更临近分布重心,复合环节日企更趋外;服务型日企更趋中,生产型日企更趋外。集聚区内服务功能型日企更多,集聚区外生产功能型的日企更多。③ 新增日企,无论单环节还是复合环节日企,就业规模均显著减小。越是临近分布重心、越是位于集聚区内的日企,平均就业规模越小。④ 大都市区范围内,集聚更利于吸引中小日企扎堆布局,更利于抑制其规模扩张冲动;日企主营业务的技术经济特点会影响分工作用的显现,隶属行业、进驻时长和独合资模式等也有显著性影响。     

Aseismic deep subduction of the Philippine Sea plate and slab window

We have made great efforts to collect and combine a large number of high-quality data from local earthquakes and teleseismic events recorded by the dense seismic networks in both South Korea and West Japan. This is the first time that a large number of Korean and Japanese seismic data sets are analyzed jointly. As a result, a high-resolution 3-D P-wave velocity model down to 700-km depth is determined, which clearly shows that the Philippine Sea (PHS) plate has subducted aseismically down to ∼460 km depth under the Japan Sea, Tsushima Strait and East China Sea. The aseismic PHS slab is visible in two areas: one is under the Japan Sea off western Honshu, and the other is under East China Sea off western Kyushu. However, the aseismic PHS slab is not visible between the two areas, where a slab window has formed. The slab window is located beneath the center of the present study region where many teleseismic rays crisscross. Detailed synthetic tests were conducted, which indicate that both the aseismic PHS slab and the slab window are robust features. Using the teleseismic data recorded by the Japanese stations alone, the aseismic PHS slab and the slab window were also revealed (Zhao et al., 2012), though the ray paths in the Japanese data set crisscross less well offshore. The slab window may be caused by the subducted Kyushu-Palau Ridge and Kinan Seamount Chain where the PHS slab may be segmented. Hot mantle upwelling is revealed in the big mantle wedge above the Pacific slab under the present study region, which may have facilitated the formation of the PHS slab window. These novel findings may shed new light on the subduction history of the PHS plate and the dynamic evolution of the Japan subduction zone.     

Complex slab structure and arc magmatism beneath the Japanese Islands

A dense nationwide seismic network recently constructed in Japan has resulted in the production of a large amount of high-quality data that have enabled the high-resolution imaging of deep seismic structures in the Japanese subduction zone. Seismic tomography, precise locations of earthquakes, and focal mechanism research have allowed the identification of the complex structure of subducting slabs beneath Japan, revealing that the subducting Philippine Sea slab underneath southwestern Japan has an undulatory configuration down to a depth of 60–200 km, and is continuous from Kanto to Kyushu without disruption or splitting, even within areas north of the Izu Peninsula. Analysis of the geometry of the Pacific and Philippine Sea slabs identified a broad contact zone beneath the Kanto Plain that causes anomalously deep interplate and intraslab earthquake activity. Seismic tomographic inversions using both teleseismic and local events provide a clear image of the deep aseismic portion of the Philippine Sea slab beneath the Japan Sea north of Chugoku and Kyushu, and beneath the East China Sea west of Kyushu down to a depth of ∼450 km. Seismic tomography also allowed the identification of an inclined sheet-like seismic low-velocity zone in the mantle wedge beneath Tohoku. A recent seismic tomography work further revealed clear images of similar inclined low-velocity zones in the mantle wedge for almost all other areas of Japan. The presence of the inclined low-velocity zones in the mantle wedge across the entirety of Japan suggests that it is a common feature to all subduction zones. These low-velocity zones may correspond to the upwelling flow portion of subduction-induced convection systems. These upwelling flows reach the Moho directly beneath active volcanic areas, suggesting a link between volcanism and upwelling.     

Contemporary crustal motion and deformation of South America plate

This paper presents the contemporary motion and active deformation of South America plate and relative motion of Nazca-South America plate using space geodetic data. The South America plate is moving at average 14.5 mm/a with an azimuth of 15.2° and shrinking in the west-east at 10.9 mm/a. The geodetic deformations of sites with respect to the South America plate are in quite good agreement with the estimated deformations from NNR-NUVEL1A, but the deformation of the western South America regions is very large.