Spatial distribution and focal mechanisms of mantle earthquakes in the Hindu Kush–Pamir region: A contorted Benioff zone

Geology ◽  
1977 ◽  
Vol 5 (11) ◽  
pp. 699 ◽  
Author(s):  
Selena Billington ◽  
Bryan L. Isacks ◽  
Mauwia Barazangi
2007 ◽  
Vol 50 (5) ◽  
pp. 1256-1264 ◽  
Author(s):  
Xiao-Ting LOU ◽  
Gui-Ling DIAO ◽  
Guo-Yang YE ◽  
Jie-Yuan NING

2011 ◽  
Vol 63 (7) ◽  
pp. 669-673 ◽  
Author(s):  
Youichi Asano ◽  
Tatsuhiko Saito ◽  
Yoshihiro Ito ◽  
Katsuhiko Shiomi ◽  
Hitoshi Hirose ◽  
...  

Приведен обзор сейсмичности Северной Евразии в 2013 г., включающей 15 регионов России и сопредельных стран. На указанной территории действовало 581 стационарная сейсмическая станция, из них 529 цифровых, 52 аналоговых и 8 сейсмических групп. Кроме того, в ряде регионов работали временные станции. Данными сетями зарегистрировано свыше 28 тыс. тектонических и около 6 тыс. вулканических землетрясений, для которых определены и опубликованы основные параметры. Для 595 землетрясений определены механизмы очагов. Согласно собранным в рамках ежегодника данным, в 2013 г. на территории Северной Евразии ощущались 506 землетрясений, о которых поступило более 1500 сообщений из более чем 934 населенных пунктов. Некоторые населенные пункты в течение года испытывали сотрясения несколько раз. Восемнадцать землетрясений были обследованы, результаты для большинства из них описаны в отдельных статьях данного выпуска Ежегодника, вместе с данными о механизмах очагов, предшествующей сейсмичности, особенностях афтершокового процесса и с привлечением элементов сейсмотектоники очаговых зон. В обзоре дан сравнительный анализ характеристик сейсмичности по всем 15 регионам. Сильнейшее в 2013 г. Охотоморское-III землетрясение 24 мая 2013 г. с Mw=8.3, произошедшее под акваторией Охотского моря на глубине h=630 км, явилось и крупнейшим за всю историю сейсмологических наблюдений среди мантийных землетрясений. Оно имело огромную площадь макросейсмического воздействия, но при этом из-за большой глубины нигде не вызвало разрушений. A review of the seismicity of Northern Eurasia in 2013, which includes 15 regions of Russia and neighboring countries, is presented. 581 stationary seismic stations operated in the territory, of which 529 digital, 52 analog stations and 8 seismic groups. In addition, temporary stations operated in some regions. These networks recorded over 28 thousand tectonic and about 6 thousand volcanic earthquakes, for which the main parameters were determined and published. Focal mechanisms have been determined for 595 earthquakes. According to the data collected as part of the yearbook, 506 earthquakes were felt in Northern Eurasia in 2013, of which more than 1500 messages were received from more than 934 settlements. Some settlements experienced shocks several times during the year. Eighteen earthquakes were inspected, the results for most of them are described in separate articles of this issue of the yearbook, together with data on the focal mechanisms, previous seismicity, features of the aftershock process and involving elements of seismic tectonics of focal zones. The review provides a comparative analysis of seismicity characteristics for all 15 regions. The strongest in 2013, the Okhotsk-III earthquake on May 24, 2013 with Mw=8.3 occurred under the Sea of Okhotsk with h=630 km, was also the largest in the history of seismological observations among mantle earthquakes. It had a huge area of macroseismic impact, while due to the great depth it did not cause destruction anywhere.


1971 ◽  
Vol 61 (2) ◽  
pp. 417-428 ◽  
Author(s):  
William Stauder

abstract The examination of the BENHAM aftershocks is extended to 162 earthquakes approximately an order of magnitude smaller than those previously studied. The spatial distribution of these smaller events is similar to that found for larger events examined by Hamilton and Healy (1969). Focal mechanisms are also similar to those of the larger aftershocks: dip-slip along northeasterly trending zones and generally strike-slip along a north-south trending zone west of the shot-point. About one third of the mechanism solutions are ambiguous, capable of either interpretation. Amplitude data are successfully used to resolve the ambiguity in about one half of these cases by selecting the solution which gives a notably lesser value of the variance, Σ (∑(Ai, obs − kAi, calc)2/N of the amplitude residuals. The value of k is related to the magnitude of the shocks. A b value of 1.09 indicates that aftershocks of the explosion follow a recurrence rate normal for regional earthquakes or aftershock sequences.


Author(s):  
Wilmer Emilio García Moreno

Colombia is region with high seismicity due to the convergence of Panama Block, Nazca and Caribbean plates with the South American Plate, however there is a complex area named The Bucaramanga Nest which was the motive of this research means of its complexity, being that there have been different studies which have not been able to explain the reason of this phenomenon, for that motive this work has as objective finding this answer by the use of 3679 earthquake information in Colombia, with a Mw higher than 3.5. Having information from all the earthquakes, they were localized on its epicenters to notice how they were distributed, after that, five lines were chosen to make, along them, The Benioff Zone, obtaining the geometry of the slabs for Nazca and Caribbean plates, knowing the angle of subduction of them and how it changed, also, thirty earthquakes near the five lines were selected to see the focal mechanisms along the slabs and knowing the fault system in The Bucaramanga Nest. Beside all it was said before, it was modeled an approximation of the subduction zones by a contour map along the studied region. At the end, it was able to reach an answer about the reason of why The Bucaramanga Nest happened, defining its vertical and lateral extension too.


1977 ◽  
Vol 41 (318) ◽  
pp. 173-182 ◽  
Author(s):  
R. Grant Cawthorn

SummaryThe petrological interpretation of the variation of K2O content with depth to the Benioff zone in orogenic magmas is complicated by several factors: (1) Magmas may not be true primary liquids but have under-gone differentiation. K2O contents, at a specific SiO2 level, will depend upon the SiO2 content of the parental magma and the natureof the crystallizing phases more than on original K2O content. (2) The depth to the Benioff zone may not give a true reflection of the depth of melting. Magmas may not be derived from the uppermost layer of subducted oceanic crust but rather the overlying upper mantle. Earthquakes may not occur in the uppermost layer of the subducted plate, but in its colder, central parts. Hence, earthquake depth may not be related to the source of the magma. (3) It is difficult to envisage how the temporal increase in K2O may occur in certain areas (e.g. Aleutian I., Fiji) if it is primarily controlled by the depth to the Benioff zone.There may be some correlation between K2O content of magmas and earthquake depth, but its cause is difficult to determine. None of the existing explanations is entirely satisfactory, and it is suggested that varying degrees of fractional crystallization may play an important role in controlling K2O contents.


Sign in / Sign up

Export Citation Format

Share Document