ImageVerifierCode 换一换
格式:DOCX , 页数:12 ,大小:27.27KB ,
资源ID:16259386      下载积分:3 金币
快捷下载
登录下载
邮箱/手机:
温馨提示:
快捷下载时,用户名和密码都是您填写的邮箱或者手机号,方便查询和重复下载(系统自动生成)。 如填写123,账号就是123,密码也是123。
特别说明:
请自助下载,系统不会自动发送文件的哦; 如果您已付费,想二次下载,请登录后访问:我的下载记录
支付方式: 支付宝    微信支付   
验证码:   换一换

加入VIP,免费下载
 

温馨提示:由于个人手机设置不同,如果发现不能下载,请复制以下地址【https://www.bdocx.com/down/16259386.html】到电脑端继续下载(重复下载不扣费)。

已注册用户请登录:
账号:
密码:
验证码:   换一换
  忘记密码?
三方登录: 微信登录   QQ登录  

下载须知

1: 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。
2: 试题试卷类文档,如果标题没有明确说明有答案则都视为没有答案,请知晓。
3: 文件的所有权益归上传用户所有。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 本站仅提供交流平台,并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。

版权提示 | 免责声明

本文(The interplay between global tectonic processes anWord文件下载.docx)为本站会员(b****6)主动上传,冰豆网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知冰豆网(发送邮件至service@bdocx.com或直接QQ联系客服),我们立即给予删除!

The interplay between global tectonic processes anWord文件下载.docx

1、The purpose of this work is to analyse the interaction betweenglobal tectonics and local scale seismicity in a selected region ofthe Mediterranean, the central Apennines.Several results have beenpublished on the modelling of tectonic processesin the Apennine regionand the study of their inuence on c

2、rustal motionsor stress andstrain accumulation using different approaches(e.g. Malinverno &Ryan 1986; Bassi & Sabadini 1994; Giunchi et al. 1994; Faccennaet al. 1996; Carminati et al. 1999, 2001; Negredo et al. 1999a,b)However, none of these has focused on the relation between tectoniceand the seism

3、ic cycle within a selected seismogenic zone. In thisworkwe study the inuence of global scale tectonics on the seismiccycle of the Colorito fault, responsible for the UmbriaMarche1997 sequence.The Apennines developed in a region affected by the collisionbetween Africa and Eurasia and by the subductio

4、n of the Adriaticlithosphere. The tectonic evolution of the chain started in theOligocene, when a collisional phase took place due to the convergencebetween the SardiniaCorsica block and the Adriatic domain(Boccalettiet al.1983). Extension, initially in a westeast and evolvingin a northwestsoutheast

5、 direction (Patacca et al. 1990), startedin the Late Oligocene with the 1 INTRODUCTIONopening of the AlgeroProvencalBasin, west of CorsicaSardinia (Rehault et al. 1984), it continuedwith the opening of the Northern Tyrrhenian Basin in the MiddleLateMiocene (Lavecchia 1988; Sartori 1989) and migrated

6、 southeastwardswith time (e.g. Spadini et al. 1995). This eastward migration through time of the extensional tectonics in the TyrrhenianBasin and of the external compressional front is a peculiarity ofthe evolution of the Apennine chain (Ricci Lucchi 1986) and hasbeen interpreted as being due to dif

7、ferent geodynamic mechanisms.Malinverno & Ryan (1986) proposed an interpretation based on amechanism of trench retreat or roll-back of the subducting Adriaticlithosphere that would cause the opening of a backarc basin. An alternative interpretation has been proposed (e.g. Wezel 1982), whichconsiders

8、 the asthenospheric upwelling related to the rifting processin the Tyrrhenian Sea, as a forcing geodynamic mechanism. Furthermore, Cavinato & De Celles (1999)proposed that the bimodal stateof stress in the Apennines is maintained by cornerow in the mantlewedge beneath the crest of the range. Subduct

9、ion in central Italy issuggested by the presence of seismicity down to 90 km (Selvaggi &Amato 1992) and by geochemical analyses of the northern Apennine arc magmatism (Serri et al. 1993). However, Spakman (1990),on the basis of tomographic results and the reduced seismicity at intermediate levels, s

10、uggested that the slab may be totally or partiallydetached, while Amato et al. (1993) interpreted the presence of ahigh-velocity body down to 200250 km as evidence of a continuousslab. It is thus clear that the tectonic setting of northern Apenninesis very complex and that anal explanation of the ro

11、le of the severalongoing processes has not been reached yet.A nite-element technique is used to model the stress patternalong a vertical cross-section in central Italy perpendicular to theApennines: this approach improves our understanding of the activetectonic processes in the region under study. I

12、n order to analysethe inuence on the stress eld from various tectonic mechanisms,several different models have been performed, each one characterized by different driving forces. We investigated the effects of thenegatively buoyant subducted Adriatic lithosphere, the effects ofthe extensional SWNE o

13、riented forces expected from the counterclockwise motion of the Adriatic Plate and the effects of small-scaleconvection at the bottom of the Tyrrhenian lithosphere driven by thechange from a passive to active rifting mode (Huismans et al.2001).The stress distribution induced in the seismogenic part

14、of the crustby each tectonic mechanism is compared with the stress pattern ofthe region deduced from earthquake focal mechanisms, boreholebreakout analysis, in situ stress measurements and young geological deformation features (Frepoli & Amato 1997; Montone et al.1999). These data are complemented b

15、y recent GPS baseline ratesobtained from new GPS receivers installed along the transect understudy.In Fig. 1 (WSM2000, Mueller et al. 2000) the trace of the modelled section is indicated by the letters A-A. Moving along this direction, from west to east, stress indicators change from extensional(red

16、 symbols) in Tuscany and in the internal sectors of the Apenninebelt, to compressional (blue symbols) in the Adriatic Basin. Similarstress maps have been compiled by Reba et al.(1992) and Montoneet al. (1999)Stress changes, obtained by modelling the seismic cycle alonga shallow low-angle normal faul

17、t, with strike perpendicular to theprole under study, have been superimposed on the stresseld generated by the different tectonic processes. The same approach alreadyused for the simulation of the Mexican subduction zone (Gardi et al.2000) has been followed in the present work, although the modellin

18、gof the seismic cycle is more realistic in the present study. In fact,the locked and free alternating phases on the fault, reproducing thestickslip process, are simulated in a different way with respectto the application carried out by Gardi et al. (2000). In that studythe locking of the fault was o

19、btained by imposing a zero x- andy-displacement to the nodes of the grid dening the fault, whilethe earthquake was simulated by imposing a xed displacement tothe same nodes in order to reproduce the dislocation. In the presentanalysis, locking is reproduced by impeding the relative motion ofthe two

20、sides of the fault but leaving the fault free to move in thexy-plane. To simulate the occurrence of an earthquake, the two sidesof the fault are left free to move one with respect to the other, along africtionless interface, driven solely by the stress accumulated duringthe loading period of the act

21、ive tectonics. The approach developedin the present study is more realistic than that in Gardi et al.(2000)and represents a substantial improvement with respect to previousmodelling. It is worth emphasizing that this new method facilitatesrelating the slip obtained during a series of subsequent eart

22、hquakesto the earthquake recurrence time and active tectonics.2 MODEL DESCRIPTIONIn order to simulate the sinking of the Adriatic Plate underneaththe Apennines and the seismic cycle on a shallow low-angle normal fault, the MARC package (MSC.Marc 2001) based on a niteelement technique has been used.

23、The simulations were performedunder a quasi-static approximation and the models are purely mechanical, since the coupling between the momentum and the temperature equations is not taken into account. Two models are considered,each one representing a 2-D vertical cross-section (Fig. 2) perpendicular

24、to the strike of the Apennines and of the UmbriaMarcheseismogenic zone, as shown in Fig. 1 by the trace A-A. The 2-Ddomain is subdivided into quadrilateral plane-strain elements, creating an irregular mesh. The element density is increased aroundthe discontinuities in order to ensure a good approxim

25、ation of thesolution. The modelled section is 400 km wide and 420 km deep.The simplied geometry of the plates and the thickness of the different layers have been dened following, for the crustal levels, theresults of the seismic line CROP-03 (e.g. Pialli et al. 1998), andfor greater depths, the results of tomographic studies (Piromallo &Morelli 1997; Chimera et al. 2003). Since the depth reached by theplunging lithosphere is still a matter of debate, two hypotheses havebeen tested: a depth of 90 km as inferred from subcrustal intr

copyright@ 2008-2022 冰豆网网站版权所有

经营许可证编号:鄂ICP备2022015515号-1