自由表面对地震辐射能的影响:以逆冲断层为例
摘要
从震源辐射的能量表象定理出发,以逆冲断层为例,定量地分析了自由表面对逆冲断层地震波辐射能量计算的影响,利用准静态有限尺度逆冲断层位错模型,准确地计算了当断层处在不同倾角、距自由表面不同深度的情形下,断层面上和自由表面位移场和应力场变化.结果表明,当断层接近地表,且倾角很小时,考虑断层同自由表面相互耦合作用的地震波总辐射能(ER)远大于由断层本身滑动位移所释放出的辐射能量(EF),后者也就是通常用于地震波能量估算的辐射能.随着断层与自由表面之间的距离进一步增加,自由表面与断层间的耦合作用也随之减小,总的辐射能与断层面上的辐射能之比(ER/EF)接近于1.目前的结果可对地震观测中存在的远场和近场视应力不一致的现象提供了部分解释,而且该成果对于近场强地面运动的准确定量计算有着十分重要的意义.
引文
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2Cocco M,Spudich P,Tinti E.On the mechanical work absorbed on faults during earthquake ruptures.AGU Monograph,Washington DC:American Geophysical Union,2006,170:237―254
3Favreau P,Archuleta R.Direct seismic energy modeling and application to the1979Imperial Valley earthquake.Geophys Res Lett,2002,30:1198,doi:1029/2002GL015968
4Kanamori H,Rivera L.Energy partitioning during an earthquake.AGU Monograph,Washington DC:American Geophysical Union,2006,170:3―14
5Chang T Y,Cotton F,Tsai Y B,et.al.Quantification of hanging-wall effects on ground motion:Some insights from the1999Chi-Chi earth-quake.Bull Seism Soc Am,2004,94(6):2186―2197,doi:10.1785/0120030233
6Lay T,Kanamori H,Ammon C J,et al.The great Sumatra-Andaman earthquake of26December2004.Science,2005,308(5725):1127―1133
7Brune J N.Particle motion in a physical model of shallow angle thrust faulting.Proc Indian Acad Sci,1996,105:197―206
8Shi B,Anooshehpoor A,Brune J N,et al.Dynamics of thrust faulting:2D lattice model.Bull Seism Soc Am,1998,88(6):1484―1494
9Madariaga R.Radiation from a finite reverse fault in a half space.Pure Appl Geophys,2003,160:555―577
10Rivera L,Kanamori H.Representations of the radiated energy in earthquakes.Geophys J Int,2005,162:148―155
11Kostrov B V.Seismic moment and energy of earthquakes,and seismic flow of rock.Izv Earth Phys,1974,1:23―40
12Abercombie R,Rice J R.Can observations of earthquake scaling constrain slip weakening.Geophys J Int,2005,162:406―424
13Rice R J,Charles G S,Parsons R.Off-fault secondary failure induced by a dynamic slip pulse.Bull Seism Soc Am,2005,95(1):103―134
14Andrews D J.Rupture dynamics with energy loss outside the slip zone.J Geophys Res,2005,110:B01307,doi:01310.01029/02004JB003191
15Kanamori H,Heaton T H.Microscopic and macroscopic physics of earthquakes.AGU Monograph,Washington DC:American Geophysical Union,2000,120:147―155
16Orowan E.Mechanism of seismic faulting in rock deformation:A symposium.Geol Soc Am Mem,1960,79:323―345
17Kanamori H,Anderson D L.Theoretical basis of some empirical relations in seismology.Bull Seism Soc Am,1975,65:1073―1095
18Scholz C.The Mechanics of Earthquakes and Faulting.New York:Cambridge Uriversity Press,1990
19Xu X,Chen W,Ma W,et al.Surface rupture of the Kunlunshan earthquake(Ms8.1),northern Tibetan Plateau,China.Seism Res Lett,2002,
73:884―892
20Freund L B,Barnett D M.A two-dimensional analysis of surface deformation due to dip-slip faulting.Bull Seism Soc Am,1976,66:667―675
21Piessens R,de Doncker-Kapenger E,Ueberhuber C W,et al.QUADPACK.A Subroutine package or automatic integration,Springer series in computational mathematics,Vol.1.New York:Springer-Verlag,1983.30122Savage J C.A dislocation model of strain accumulation and release art a subduction zone.J Geophys Res,1983,88:4984―4996
23Lee W H K,Shin T C,Kuo K W,et al.CWB free-field strong-motion data from the921Chi-Chi earthquake:Volume1.Digital acceleration files on CD-ROM,pre-publication version(December6,1999),Seismology Center,Central Weather Bureau,Taipei,1999
24Brune J N,Thatcher W.Strength and energetics of active fault zones.In:Lee W H K,Kanamori H,Jennings P,et al,eds.International Hand-book of Earthquake and Engineering Seismology.San Diego,CA:Academic Press,2002.81A:569―588
25Ni S,Brune J N,Choy G,et al.Local and teleseismic estimates of radiated energy and apparent stress from the Chi-Chi,Taiwan earthquake:Evidence or inertial detachment of the hanging wall from the footwall in thrust faulting.Eos Trans AGU,1999,80(Fall Meet Suppl),Abstract:S32H-15
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