Rupture process of large earthquakes in the northern Mexico subduction zone

The Cocos plate subducts beneath North America at the Mexico trench. The northernmost segment of this trench, between the Orozco and Rivera fracture zones, has ruptured in a sequence of five large earthquakes from 1973 to 1985; the Jan. 30, 1973 Colima event (M _s 7.5) at the northern end of the segment near Rivera fracture zone; the Mar. 14, 1979 Petatlan event (M _s 7.6) at the southern end of the segment on the Orozco fracture zone; the Oct. 25, 1981 Playa Azul event (M _s 7.3) in the middle of the Michoacan gap; the Sept. 19, 1985 Michoacan mainshock (M _s 8.1); and the Sept. 21, 1985 Michoacan aftershock (M _s 7.6) that reruptured part of the Petatlan zone. Body wave inversion for the rupture process of these earthquakes finds the best: earthquake depth; focal mechanism; overall source time function; and seismic moment, for each earthquake. In addition, we have determined spatial concentrations of seismic moment release for the Colima earthquake, and the Michoacan mainshock and aftershock. These spatial concentrations of slip are interpreted as asperities; and the resultant asperity distribution for Mexico is compared to other subduction zones. The body wave inversion technique also determines theMoment Tensor Rate Functions; but there is no evidence for statistically significant changes in the moment tensor during rupture for any of the five earthquakes. An appendix describes theMoment Tensor Rate Functions methodology in detail.The systematic bias between global and regional determinations of epicentral locations in Mexico must be resolved to enable plotting of asperities with aftershocks and geographic features. We have spatially shifted all of our results to regional determinations of epicenters. The best point source depths for the five earthquakes are all above 30 km, consistent with the idea that the down-dip edge of the seismogenic plate interface in Mexico is shallow compared to other subduction zones. Consideration of uncertainties in the focal mechanisms allows us to state that all five earthquakes occurred on fault planes with the same strike (N65°W to N70°W) and dip (15±3°), except for the smaller Playa Azul event at the down-dip edge which has a steeper dip angle of 20 to 25°. However, the Petatlan earthquake does prefer a fault plane that is rotated to a more east-west orientation—one explanation may be that this earthquake is located near the crest of the subducting Orozco fracture zone. The slip vectors of all five earthquakes are similar and generally consistent with the NUVEL-predicted Cocos-North America convergence direction of N33°E for this segment. The most important deviation is the more northerly slip direction for the Petatlan earthquake. Also, the slip vectors from the Harvard CMT solutions for large and small events in this segment prefer an overall convergence direction of about N20°E to N25°E.All five earthquakes share a common feature in the rupture process: each earthquake has a small initial precursory arrival followed by a large pulse of moment release with a distinct onset. The delay time varies from 4 s for the Playa Azul event to 8 s for the Colima event. While there is some evidence of spatial concentration of moment release for each event, our overall asperity distribution for the northern Mexico segment consists of one clear asperity, in the epicentral region of the 1973 Colima earthquake, and then a scattering of diffuse and overlapping regions of high moment release for the remainder of the segment. This character is directly displayed in the overlapping of rupture zones between the 1979 Petatlan event and the 1985 Michoacan aftershock. This character of the asperity distribution is in contrast to the widely spaced distinct asperities in the northern Japan-Kuriles Islands subduction zone, but is somewhat similar to the asperity distributions found in the central Peru and Santa Cruz Islands subduction zones. Subduction of the Orozco fracture zone may strongly affect the seismogenic character as the overlapping rupture zones are located on the crest of the subducted fracture zone. There is also a distinct change in the physiography of the upper plate that coincides with the subducting fracture zone, and the Guerrero seismic gap to the south of the Petatlan earthquake is in the wake of the Orozco fracture zone. At the northern end, the Rivera fracture zone in the subducting plate and the Colima graben in the upper plate coincide with the northernmost extent of the Colima rupture zone.     

南极海冰、冰穴和冰川冰及其对水团形成和变性的作用

本文利用前人的成果及笔者1992/1993年的南极海冰观测和收集的资料以及水文观测资料数据阐述了南极海冰的特性,特别是南极海冰过程、冰穴以及冰川冰对南极水团(南极表层水、南极底层水、南极陆架水、南极中层水以及南极冰架水)的形成和变性所起的特殊作用。 南极海冰覆盖面积的年际变化,夏季最大年份是最小年份的2倍多,冬季年间变化较小,最大仅为20％;但其季节变化非常大,冬季平均覆盖面积通常是夏季的5倍。南极海冰对大气-海洋间相互作用有重大影响,特别是深海洋区中冬季的结冰和发育造成的垂向对流、夏季的融化是形成南极表层水(含南极冬季水和南极夏季表层水),进而形成南极中层水的主要原因;南极陆架区的的海冰兴衰过程是形成南极陆架水的直接原因,它与变性南极绕极深层水混合并受到冰川冰的进一步冷却作用,成为形成南极底层水的主要水团;南极冰架底部的冷却、融化和冰架以下水体的结冰作用形成的高盐对流过程产生的南极冰架水,亦是形成南极底层水的贡献者。 冰穴是70年代以来卫星观测的重大发现。对其形成和对大气、海洋的影响作用尚不完全清楚,初步的研究成果表明,冰穴中产生的热盐对流对南极水团的形成、变性、大洋深层的翻转以及海洋-大气间的热量传输和气体交换起有非常重要的作用。     

钾霞石制备体系碱性滤液的利用技术

为处理钾长石水热制备钾霞石所产生的碱性滤液,本文采用水热法,考察了氢氧化铝溶解时间、晶化时间、晶化温度、水碱比对钾霞石产率和白度的影响,并对合成钾霞石物相进行了表征。结果表明,合成钾霞石的最佳条件为,氢氧化铝溶解时间为1.5 h,晶化时间为4 h,晶化温度280℃,水碱比为1.8。XRD结果表明,产物为钾霞石粉体。傅里叶变换红外光谱表明,Al(OH)₃中的Al在水热条件下进入到Si—O骨架中形成了Si—O—Al官能团,从而印证了钾霞石的合成。差热分析结果表明,合成钾霞石具有良好的热稳定性。氮气吸附结果表明,合成钾霞石比表面积为5.18 m²/g,平均孔径为32.98 nm。实现了钾长石水热制备钾霞石所剩碱性滤液的资源化利用,并为钾长石水热制备钾霞石提供了一种母液循环的思路,使水热制备钾霞石工业化成为一种可能。     

Research on temporal and spatial distribution, evolutionary character and mechanism of crustal deformation field before and after the Tangshan earthquake

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The mass accommodation coefficient of ammonia on water

The mass accommodation coefficient of ammonia gas on water has been determined by measuring the absorption rate of 50–200 ppm NH₃ in one atm of air or helium into a liquid jet of 97 µm diameter as function of the exposed jet length, and comparing the results with numerical simulations which treat as the only free parameter. The model considers in detail transport of NH₃ by molecular diffusion, penetration of the gas/water interface, hydrolysis in the acidified water, and transport of the solutes from the surface into the jet. A correction is applied for the time evolution of the jet surface speed, using literature data on the fluid mechanics of liquid jets. The result of nine sets of independent measurements is

硫铅酸盐“S”型瞬凝水泥干法护壁堵漏技术研究

介绍了硫铝酸盐“Ｓ”型瞬凝水泥干法者漏时使用的配方,阐述了输送工具和扫孔钻具的设计以及灌注工艺技术。     

MODERNIZATION PROCESS IN HISTORICAL ASIAN CITIES AND THEIR CHARACTERISTICS: A COMPARATIVE STUDY ON SEOUL, TOKYO AND BEIJING

Thspaperwaspresatedatthe"94SeoulIntemationalSyInPosiumonCityandffistory"heldonOCtober27to28,l994andthenpublishedinTheJoumaIofSeouIShndesVo.IV.Thepresentvisionhasbeenslighlyrevised.Bejing,SeoulandTokyoarecapitalsofthreeneighbouringcoUnnesinNortheastAsia,wh…     

The circumstellar shells of carbon miras

The relation between mass loss rate and pulsation period in carbon Miras is discussed. The dust mass loss rate is very low (about 2 × 10^–10 M/yr) up to aboutP = 380 days, where there is a sudden increase. ForP > 400 days there is a linear relation between logM andP. The change in the mass loss rate near 380 days may be related to radiation pressure on dust becoming effective in driving the outflow.     

中国大陆第四纪地壳运动时程

本文从中国大陆有代表性的青藏高原、黄土高原、三峡地区着手,进行了新构造运动剖析。并结合全国火山活动期次,总结出中国大陆第四纪地壳运动的时程变化。从而为进一步探讨新构造运动特点和规律,为国民经济建设及人类生存环境提供了一定的地质背景资料。     

膜分离技术的应用及发展趋势

综述世界和中国膜分离技术的发展，并对膜分离技术的基本特性、技术特点、膜材料、分类及膜分离装置进行了简单介绍；并介绍了膜分离法在化工及石油工业、食品工业、医药工业和医疗设备、生物技术和环境工程中的应用，并分析了膜分离技术将会在膜材料、新的膜过程和集成膜过程3个方面的发展趋势。同时指出如果能解决膜产品的价格、膜污染和膜分离性能的提高这3个膜的制约因素，膜分离技术将在人类社会的发展史上起到不可替代的作用。