Seamount Characteristics and Mine-Site Model Applied to Exploration- and Mining-Lease-Block Selection for Cobalt-Rich Ferromanganese Crusts

Regulations are being developed through the International Seabed Authority (ISBA) for the exploration and mining of cobalt-rich ferromanganese crusts. This paper lays out geologic and geomorphologic criteria that can be used to determine the size and number of exploration and mine-site blocks that will be the focus of much discussion within the ISBA Council deliberations. The surface areas of 155 volcanic edifices in the central equatorial Pacific were measured and used to develop a mine-site model. The mine-site model considers areas above 2,500 m water depth as permissive, and narrows the general area available for exploration and mining to 20% of that permissive area. It is calculated that about eighteen 100 km² exploration blocks, each composed of five 20 km² contiguous sub-blocks, would be adequate to identify a 260 km² 20-year-mine site; the mine site would be composed of thirteen of the 20 km² sub-blocks. In this hypothetical example, the 260 km² mine site would be spread over four volcanic edifices and comprise 3.7% of the permissive area of the four edifices and 0.01% of the total area of those four edifices. The eighteen 100 km² exploration blocks would be selected from a limited geographic area. That confinement area is defined as having a long dimension of not more than 1,000 km and an area of not more than 300,000 km².     

Marine protected areas in Australia: Towards a coordinated rock lobster industry position

Plans by government to accelerate the establishment of a national representative system of marine protected areas (NRSMPAs) in Australia have caused increasing disquiet within the fishing industry. Rock lobster fishers have raised concerns regarding plans to establish large “multiple‐use” MPAs that may or may not contain a substantial no‐take component in the continental shelf waters adjacent to the coast. Key industry concerns including the potential impacts on present and future harvest rates are examined. The industry response to government MPA policy in each of the major jurisdictions is outlined. An industry position developed at the National Rock Lobster Congress in Perth, Western Australia (September 2003) is put forward. The position advocates the need for an adjustment scheme to account for displaced effort, the need for government commitment to the development of management plans that include the long‐term monitoring of all MPAs, and the need for a thorough risk assessment process to be conducted before the establishment of an MPA. The issues raised in this paper should be relevant to the establishment of MPAs in an international context.     

Species and plant community reorganization in the Trans-Mexican Volcanic Belt under climate change conditions

This study analyzes six vegetation communities in relation to current climatic parameters and eight climate change scenarios along an elevation gradient extending from 2,710 m to 4,210m in the Trans-Mexican Volcanic Belt. The projected movements of 25 plant species with the current restricted or wide altitudinal distributions were also modeled. To relate climatic parameters to the species and communities, a Precipitation/Temperature(P/T)index was used both for the current and the different climate-change scenarios. The temperatures are expected to increase by 1.1°C to 1.7°C by 2020 and by2°C to 3°C by 2050. A decrease of 4% to 13% in the annual precipitation is expected for the 2020 horizon,and a reduction between 3% and 20% is expected for2050. The reductions in water availability were projected for all altitude levels and plant communities.The most marked reduction was under the HADLEYA2 scenario, in which the lower limit of the altitudinal range increased from 2,710 to 3,310 m(2050 horizon)with reductions in the P/T index between 36% and39% compared to the current climate. Most plant species tended to shift their distribution from 200 to300 m upward in the 2020 temporal horizon scenarios. The Pinus hartwegii, Alnus jorullensis and Pinus montezumae communities would have a shorter altitudinal range as they move upward and merge with the remaining species at the higher altitudinal range. For the 2050 temporal horizon,30% of the species, primarily those from the higher altitudinal range, would disappear because their P/Tindex values would be above the limit of plant survival(4,210 m).     

济南市燕翅山铁矿采空区稳定性分析评价

济南燕翅山铁矿已闭坑多年,遗留大量的采空区潜在地面塌陷、山体崩塌及裂缝隐患,对当地人民群众生命财产安全构成威胁。该文对采空区稳定性进行了分析计算,并根据研究区实际,提出了主要地质灾害治理方法和措施建议。     

长江上游区域蒸发皿蒸发量变化及其对水分循环的影响

利用长江上游最近30年(66个测站)蒸发皿蒸发量和最近50年(90个测站)的7种气象要素,分析了蒸发皿蒸发量的区域变化趋势和影响蒸发皿蒸发量变化的因素;针对7个水文站的年径流量变化,探讨了蒸发皿蒸发量变化后对水分循环的影响.结果表明,长江上游蒸发皿蒸发量的变化可以划分为三个分区,研究区域东西两侧(青藏高原和大巴山一带)为显著减少区,分别命名为RⅠ和RⅡ,中间(云贵高原北部到黄土高原南缘以及由二者包围的四川盆地一带)为显著增大区,命名为RⅢ区.影响区域蒸发皿蒸发量变化的原因各有不同,青藏高原一带(RⅠ区)蒸发皿蒸发量减少的原因可归结于太阳辐射强度和风动力扰动减弱所致.大巴山一带(RⅡ区)减少原因是太阳辐射强度、风动力扰动强度、湿度条件都在显著下降所引起的.云贵高原到四川盆地一带(RⅢ区)蒸发皿蒸发量增加是环境气温强烈升高,导致其上空大气水汽含量显著减少,大气很干燥,引发蒸发过程加强所致.蒸发皿蒸发量发生变化的直接后果就是导致水分循环强弱发生变化,对于RⅠ区,尽管蒸发皿蒸发量减少,由于降水量和径流量增加的作用,这一区域的水分循环有所加强.在RⅡ区,降水量、径流量和蒸发量都在减少,因此RⅡ区水分循环显著减弱.在RⅢ区,降水量和径流量同时减少,而蒸发量增大,水量消耗增大,因此RⅢ区水分循环有减弱趋势.     

南海北部海底沉积物在温度变化下的三种声速类型

研究南海北部海底沉积物温度变化状态下声速性质,得出以下结论:(1) 南海北部海底沉积物具有声速温度正增长(STPIK)、声速温度负增长(STNIK)和声速温度波动(STWK)三种类型,后两种类型在世界其他范围内海域未见报道.(2) 声速温度正增长类型和声速温度负增长类型沉积物的温度变化对声速影响都具有十分显著的线性关系,但是原状样品由于组成不均匀性,增大了声速的非线性变化.(3)南海北部海底沉积物的孔隙度、密度等主要物理参数差异不明显,难以直接解释三类样品的温度-声速性质的不同.(4)对于STPIK类型沉积物,理论分析与实验结果的统一性,可以运用海底沉积物与海水声速比进行校正不同温度状态下的海底沉积物的声速.(5)对于STNIK和STWK类型沉积物,需要深入研究,从理论和实验角度揭开其机理和成因.海底沉积物声速-温度特性研究将为提高南海北部海域天然气水合物声学探测精度和准确度提供声速性质依据.     

青藏高原东缘变形机制的讨论: 来自数值模拟结果的限定

青藏高原东缘的地壳结构是两种主流青藏高原隆升模式争辩的焦点之一.中下地壳流曾经被认为是高原东缘隆升的主要构造驱动力,但是中上地壳之间低阻低速层的发现及其与2008 M_S8.0汶川地震良好的对应关系表明,高原东缘具有向东刚性挤出的可能性.然而大部分关于龙门山断裂的数值模拟仍建立在下地壳流的基础上,仅将低阻低速层作为断裂的延续或是弱化地壳物性参数的软弱层,而非能够控制块体滑动的"解耦层",也没有考虑到刚性块体变形中的断裂相互作用.本文建立了包含相互平行的龙门山断裂与龙日坝断裂的刚性上地壳模型,用极薄的低阻低速层作为块体滑动的解耦带,采用速率相关的非线性摩擦接触有限元方法,基于R最小策略控制时间步长,计算了在仅有侧向挤压力作用下,低阻低速层对青藏高原东缘的刚性块体变形和断裂活动的作用.计算结果显示,低阻低速层控制了刚性块体的垂直变形和水平变形分布特征.在侧向挤压力的持续作用下,在低阻低速层控制下的巴颜喀拉块体能够快速隆升,而缺乏低阻低速层的四川盆地隆升速度和隆升量均极小,隆升差异集中在龙门山断裂附近,使其发生应力积累乃至破裂.龙日坝断裂被两侧的刚性次级块体挟持着一起向南东方向运动,但该断裂的走滑运动分解了绝大部分施加在块体边界上的走滑量,使得相邻的龙门山次级块体的走滑分量遽然减少,也使得龙门山断裂表现出以逆冲为主,兼有少量走滑的运动性质.本文所得的这些计算结果显示了在缺乏中下地壳流,仅在低阻低速层解耦下刚性块体隆升过程及相关断裂活动,提供了青藏高原东缘刚性块体挤出的可行性,为青藏高原东缘隆升机制的研究讨论提供了重要依据.     

海洋岩石圈板块有效弹性厚度研究

本文在前人研究大陆岩石圈板块有效弹性厚度的基础上,建立研究海洋岩石圈板块有效弹性厚度的理论模型,推导出与大陆岩石圈不同的海洋岩石圈板块响应函数 Z(k,T_e) 理论计算公式.并分析海洋岩石圈板块响应函数 Z(k,T_e) 的特点.文中对实际的海洋测量数据的响应函数 Z(k,T_e) 进行计算和分析,估算我国南海南沙海域和南海中央海盆岩石圈板块有效弹性厚度分别约为10 km和6~7 km.     

东昆仑断裂带东部塔藏断裂地震地表破裂特征及其构造意义

The East Kunlun fault zone is located in the northern margin of the Bayan Har block. The study of earthquake rupture behavior in the fault zone is of importance for understanding the future seismic risk in northwest Sichuan. A number of geological field investigations, typical micro topography DGPS measurements and sample dating show that the earthquake activity of the East Kunlun fault zone extends to the north boundary of Zoige basin, a segment known as the Luocha segment of Tazang fault. In the satellite image, the segment is seen clearly as gray and yellow strips. The earthquake deformation zone mainly features fault scarp, valleys on the slope, offset gullies and terraces, linear distribution of plants, waterfall, fault spring, fault sag pond, and landslide, collapse and talus associated with surface rupturing. These phenomena are distributed intermittently along the re-existing fault and form a ～50km-long inverse L-shaped deformation zone. Fault activities caused left-lateral offset of gullies and terraces, with horizontal displacement concentrated at 5.5m~6m, 18m～23m, 68m～75m, and 200m～220m, respectively. The recent earthquake occurred between 340±30～500±30BP. The macro epicenter is located 5km～7km northwest of Benduo village, with magnitude of MW7.3～7.4, maximum coseismic displacement of 6m, horizontal displacement 5.5m～6m and vertical displacement 0.2m～0.5m, being in a proportion of 5∶1～10∶1. These phenomena show that the Tazang fault is the causative fault of this earthquake. The fault is a Holocene active fault and was dominated recently by left-lateral movement with a small amount of thrust component under compressive shear stress. This characteristic is similar to the movement in other segments of the East Kunlun fault zone. The results of this study support the "continental escape" model.     

2007年宁洱6.4级地震序列精定位

Five mobile digital seismic stations were set up by the Earthquake Administration of Yunnan Province near the epicenter of the main shock after the Ning’er M6.4 earthquake on June 3, 2007. In this paper, the aftershock sequence of the Ning’er M6.4 earthquake is relocated by using the double difference earthquake location method. The data is from the 5 mobile digital seismic stations and the permanent Simao seismic station. The results show that the length of the aftershock sequence is 40km and the width is 30km, concentrated obviously at the lateral displacement area between the Pu’er fault and the NNE-trending faults, with the majority occurring on the Pu’er fault around the main shock. The depths of aftershocks are from 2km to 12km, and the predominant distribution is in the depth of 8～10km. The mean depth is 7.9km. The seismic fault dips to the northwest revealed from the profile parallel to this aftershock sequence, which is identical to the dip of the secondary fault of the NE-trending Menglian-Mojiang fault in the earthquake area. There are more earthquakes concentrated in the northwest segment than in the southeast segment, which is perhaps related to the underground medium and faults. The depth profile of the earthquake sequence shows that the relocated earthquakes are mainly located near the Pu’er fault and the seismic faults dip to the southwest, consistent with the dip of the west branch of the Pu’er fault. In all, the fault strike revealed by earthquake relocations matches well with the strike in the focal mechanism solutions. The main shock is in the top of the aftershock sequence and the aftershocks are symmetrically distributed, showing that faulting was complete in both the NE and SW directions.