The CTBT and advances in earth science     

David Booth  Peter Maguire 《Astronomy& Geophysics》2002,43(2):2.33-2.34

David Booth and Peter Maguire report on a two-day meeting organized by the Royal Astronomical Society and the British Geophysical Association, that showed how scientific challenges generated by the Comprehensive Nuclear Test Ban Treaty have been addressed, and how they continue to stimulate advances in earth science.  相似文献   

On the upper mantle beneath the Kenya Rift     

R. Masotti  P. K. H. Maguire †  J. Mechie † 《Geophysical Journal International》1996,126(2):579-592

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A crustal seismic velocity model for the UK, Ireland and surrounding seas   总被引：1，自引：0，他引：1  

Annabel Kelly  Richard W. England  Peter K. H. Maguire 《Geophysical Journal International》2007,171(3):1172-1184

A regional model of the 3-D variation in seismic P -wave velocity structure in the crust of NW Europe has been compiled from wide-angle reflection/refraction profiles. Along each 2-D profile a velocity–depth function has been digitised at 5 km intervals. These 1-D velocity functions were mapped into three dimensions using ordinary kriging with weights determined to minimise the difference between digitised and interpolated values. An analysis of variograms of the digitised data suggested a radial isotropic weighting scheme was most appropriate. Horizontal dimensions of the model cells are optimised at 40 × 40 km and the vertical dimension at 1 km. The resulting model provides a higher resolution image of the 3-D variation in seismic velocity structure of the UK, Ireland and surrounding areas than existing models. The construction of the model through kriging allows the uncertainty in the velocity structure to be assessed. This uncertainty indicates the high density of data required to confidently interpolate the crustal velocity structure, and shows that for this region the velocity is poorly constrained for large areas away from the input data.  相似文献   

Crustal structure of the East African Rift zone     

R.E. Long  K. Sundaralingam  P.K.H. Maguire 《Tectonophysics》1973,20(1-4):269-281

A review of seismological data on the crustal structure of the East African Rift zone is presented. The only refraction line is that along the Gregory Rift, which indicates a 7.5 km/sec refractor which is presumed to be the Moho. The bulk of data is provided by surface-wave dispersion studies. Some preliminary measurements of crustal and sub-Moho velocities using the University of Durham array at Kaptagat in Kenya are included.

There is now a growing body of evidence that the crust is generally of shield type over the whole rift zone. The exception is along the axis of the Gregory Rift, where a low-velocity Moho and some crustal modification is apparent. This is presumably the result of magma intrusions and suggests some crustal separation along this section of the rift. Sub-Moho velocities are probably normal outside the rifts themselves, though anomalously low upper-mantle velocities are to be associated with rifting. There is firm evidence for thinning of the lithosphere along the eastern branch of the rift. A cross-section of the Gregory Rift which is consistent with the current data is presented.  相似文献   

Relocation of Swarm Events in the June 1987 Earthquake Sequence from the Lake Aswan Area in Egypt     

A. Hassoup  P. Denton  P. Maguire  G. Hassib 《Pure and Applied Geophysics》2003,160(7):1245-1257

--We have examined the digital waveform data and relocated a number of events within the June 1987 earthquake swarm, which occurred beneath the northern part of Lake Aswan, 70 km southwest of the Aswan High Dam in Egypt. This swarm occurred between June 17th and 19th with a maximum magnitude event of "M_L"=3.5.¶Cross correlation between a chosen master and the analyzed events has been carried out on seismograms from stations of the Aswan network. The cross correlation demonstrates the presence of a difference in both the P wave ((t_p) and the S wave ((t_s) arrival times at each station in the network relative to the arrival times of the master event at the same stations. (t_p ranges between т.15 and 0.11 second, while (t_s ranges between т.17 and 0.11 second.¶The primary interpretation is that the se time differences represent an error in the manually picking arrival times. Then, (t_p and (t_s values for each event result from a change in the hypocentral parameters from those of the master event, assuming the P- and S-wave velocity distribution remains constant during the swarm activity. This interpretation enables us to determine the relative distribution of hypocenters with respect to the hypocentral location of the master event. We present the results from a swarm of 9 events demonstrating they originate from a nearly unique location, rather than the zone identified from the preliminary locations which used manually picked onset times.  相似文献   

Grenville age of basement rocks in Cape May NJ well: new evidence for Laurentian crust in u.s. Atlantic Coastal Plain basement Chesapeake terrane     

Robert E. Sheridan  Timothy J. Maguire  Mark D. Feigenson  Lina C. Patino  Richard A. Volkert 《Journal of Geodynamics》1999,27(4-5)

The Chesapeake terrane of the U.S. mid-Atlantic Coastal Plain basement is bounded on the northwest by the Salisbury positive gravity and magnetic anomaly and extends to the southeast as far as the Atlantic coast. It underlies the Coastal Plain of Virginia, Maryland, Delaware and southern New Jersey. Rubidium/ Strontium dating of the Chesapeake terrane basement yields an age of 1.025±0.036 Ga. This age is typical of Grenville province rocks of the Middle to Late Proterozoic Laurentian continent. The basement lithologies are similar to some exposed Grenville-age rocks of the Appalachians. The TiO₂ and Zr/P₂O₅ composition of the metagabbro from the Chesapeake terrane basement is overlapped by those of the Proterozoic mafic dikes in the New Jersey Highlands. These new findings support the interpretation that Laurentian basement extends southeast as far as the continental shelf in the U.S. mid-Atlantic region. The subcrop of Laurentian crust under the mid-Atlantic Coastal Plain implies unroofing by erosion of the younger Carolina (Avalon) supracrustal terrane. Dextral-transpression fault duplexes may have caused excessive uplift in the Salisbury Embayment area during the Alleghanian orogeny. This extra uplift in the Salisbury area may have caused the subsequent greater subsidence of the Coastal Plain basement in the embayment. © 1999 Elsevier Science Ltd. All rights reserved.  相似文献   

The Structure on the Western Flank of the Gregory Rift (Kenya). Part I. The Crust     

P. K. H. Maguire  R. E. Long 《Geophysical Journal International》1976,44(3):661-675

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Draft eurocode 8—sample seismic force calculations for discussion purposes     

C. J. Hayhurst  J. R. Maguire 《地震工程与结构动力学》1988,16(5):775-779

Draft Eurocode 8 (Common Unified Rules for Structures in Seismic Regions¹) is open for study and comment until the latter part of 1989. This paper presents sample seismic force calculations for an idealized building, to illustrate the differing forces which result from the alternative calculation methods allowed. It is tentatively suggested that part of the Draft be revised as a result of the above.  相似文献   

吉林省伊通地区橄榄岩包体的同位素特征与岩石圈地幔时代   总被引：6，自引：2，他引：4  

周琴  吴福元  储著银  葛文春 《岩石学报》2010,26(4):1241-1264

吉林省伊通新生代火山群中大孤山所伴生的东小山火山含有丰富的地幔橄榄岩包体,详细的岩石学和矿物学工作显示,这些包体的主要岩石类型为尖晶石二辉橄榄岩,含有少量的方辉橄榄岩和异剥橄榄岩。包体的结构类型多样,包括粒状变晶结构、碎斑状结构、糜棱结构和筛状变晶结构。主量元素及矿物化学资料表明,这些地幔橄榄岩包体大都比较饱满,说明其所经历的部分熔融程度较低。微量元素显示,包体在形成以后经受过不同程度地幔交代作用的影响。矿物平衡温度计算结果表明包体的平衡温度为989～1142℃,来源深度约为40～70km。Sr-Nd-Hf同位素资料反映二辉橄榄岩包体具有亏损地幔的特征。Re-Os同位素资料显示上述岩石圈地幔的主体形成于显生宙期间,少量具有中元古代Re亏损年龄的样品所代表的古老地幔与本区上覆地壳成因无关,可能是软流圈中固有的较古老的大陆岩石圈地幔。  相似文献   

A new dimension for UK seismology     

Peter Maguire 《Astronomy& Geophysics》2001,42(6):6.23-6.25

The award of £2.1m for UK seismology has resulted in a powerful new suite of field instruments and the data management structure necessary for their efficient use. Peter Maguire reports, on behalf of the SEIS-UK team.  相似文献