2015/9/16 Chapter1 Chapter One 1.1 Causesand Types of Earthquake 1.2 Seismic Waves and Propagation Earthquake and 1.3 Earthquake Magnitude and Intensity Ground motions 14 Seismicity in the world 1.5 Seismic Fortification for Building Structures 1.1 Causes and Types of Earthquake Plate Tectonics Earth's crust.mantle earth Plate Tectonics Plate Tectonics Earth's crust,mantle,core 1
2015/9/16 1 Chapter One Earthquake and Ground motions 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 1 1.1 Causes and Types of Earthquake 1.2 Seismic Waves and Propagation 1.3 Earthquake Magnitude and Intensity 1.4 Seismicity in the World 1.5 Seismic Fortification for Building Structures 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 2 Chapter 1 • Earthquakes Causes Earthquakes may results from a number of natural and humaninduced phenomena. • Include - Plate Moving → Tectonic Earthquake (90%) - Volcanic Activity → Volcanic Earthquake - Collapse → Collapse Earthquake - Large Reservoir-induced Earthquake - Nuclear Explosion-induced Earthquake 1.1 Causes and Types of Earthquake 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 3 Plate Tectonics Earth's crust, mantle, core http://en.wikipedia.org/wiki/Structure_of_the_Earth 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 4 Crust Mantle Core • 16~40 km • most earthquakes occurred • rocks • 2900 km • 5/6 of the earth’s volume • transfer shear wave • solid • 3500 km • liquid + solid http://en.wikipedia.org/wiki/Structure_of_the_Earth 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 5 Plate Tectonics Earth's crust, mantle, core http://edition.cnn.com/2012/10/01/tech/mantle-earth-drill-mission 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 6 Plate Tectonics
2015/9/16 Plate Moving Plate Moving Flg-13 Fault Fg.1.2 Tech Fault ty in
2015/9/16 2 • Collisions between adjacent lithospheric plates, • destruction of the slab-like plate, • spreading along mid-oceanic ridges 7 Plate Moving 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 8 Plate Moving Fig.1.3 Continued drift of the Indian plate towards Asian plate causes major Himalayan earthquakes 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 9 Fig.1.2 Tectonic plate and world-wide distribution of earthquakes Earthquake Occurred Don’t look at me like that…, It’s not my fault! 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 10 Fault In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement along the fractures as a result of earth movement. Large faults within the Earth's crust result from the action of plate tectonic forces. Fracture: interrupt, break, or destroy Crust: the outer layer of the Earth Tectonic: relation to the structure or movement of the earth's crust 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 11 Fault Fig.1.3 Sketch of the earth’s crust 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 12 • Field observations show that abrupt changes in the structure of rocks are common. • Such offsets of geological structure are called faults. • Faults are causes rather than results of earthquakes
2015/9/16 Normal Fault Reverse Fault al fauit is one Strike-Slip Fault Can you distinguish the fault? 日 teral fault.inve Terminology Earthquakes are e classified as ng to focal dept focal depthkm 3
2015/9/16 3 • A normal fault is one in which the rock above the inclined fault surface moves downward relative to the underlying crust. 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 13 Normal Fault A reverse fault is one in which the crust above the inclined fault surface moves upward relative to the block below the fault. 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 14 Reverse Fault • A strike-slip fault ， sometimes called a transcurrent fault or lateral fault, involves displacements of rock laterally, parallel to the strike. 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 15 Strike-Slip Fault The San Andreas Fault, a right-lateral strike-slip fault, caused the massive 1906 San Francisco earthquake Source From: http://en.wikipedia.org/wiki/Fault_(geology) Can you distinguish the fault? Himalaya Mountains 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 16 Terminology 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 17 震中 震 源 深 度 震源距 震中距 Earthquakes are classified as: （according to focal depth） • Shallow Earthquakes focal depth 300 km 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 18
2015/9/16 Earthquakes are also classified as: 1.2 Earthquake waves and propagation (according to time sequence) Body waves☐ P waves S waves A fe Body wa oture zone and within a body of solid rod 00980 0888 Pwaves☐ S waves P waves parellel to the direction of propagation of the wave v n of ware 密 Surface waves Rayleigh Waves R waves☐ Surface waves- L waves c movement
2015/9/16 4 Earthquakes are also classified as: (according to time sequence) • Foreshock A few earthquakes are proceeded by smaller from the source area, which can be used to predict the main shock. • Aftershock Large earthquakes are sometimes followed by incredible numbers of them, which can results the damaged building destructed. 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 19 Body waves, originating at the rupture zone and traveling within a body of solid rock. 1.2 Earthquake waves and propagation 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 20 Body waves P waves S waves Video 1 P waves parallel to the direction of propagation of the wave. •The motion of the P wave is the same as that of a sound wave, it alternately pushes (compresses) and pulls (dilates) the rock. • The P waves are able to travel through both solid rock and liquid material, such as volcanic magma or the water of the oceans. Direction of wave travel Direction of vibration 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 21 P waves • P for Primary Direction of wave travel Direction of vibration •S waves produce an upand-down and side-toside motion of the earth that shakes the ground vertically and horizontally at right angles to the direction of wave travel. •S for Secondary •S waves cannot propagate in the liquid parts of the earth, such as the oceans, and their amplitude is significantly reduced in liquefied soil. 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 22 S waves • Their motion of surface waves is mainly at or near ground surface. • two types: • Rayleigh waves or R waves • Love waves or L waves. 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 23 Surface waves R waves L waves Surface waves Rayleigh Waves • Rayleigh wave move both vertically and horizontally in a vertical plane, in which the waves are traveling and exhibit elliptic movement. 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 24
2015/9/16 Love waves□ 1.2 Earthquake waves and propagation -g-a-月 woi图 网 Q2:When we know>V What can we do? 8gonquaaPaetae Earthquake Warning System 上.20-万 Eg. g11-2y Strong Shaking Expected Early Warning 1.An earthquake warning system is a system of accelerometers.communication.computers.and alarms.that s devised for regional notification of a substantial V quake while it is in progress This is not the same as earthquake prediction,which is urrently inca of produding de before earthquake attack. Earthquake Records .ELCentro(US earthquake record) 5
2015/9/16 5 Love waves Love wave moves the ground side to side in a horizontal plane parallel to the earth’s surface. No vertical displacement. Q1: What can we observe from the different speed of the four kinds of waves? Q2: When we know VP>VS>VL>VR,What can we do? 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 25 Video 1 • For general material, during earthquakes P waves travel faster than S waves. • The propagation velocities of P and S waves depend on the density and elastic properties of the rocks and soil through which they pass. 1.2 Earthquake waves and propagation E G Vp 2 (1 )(1 2 ) (1 ) E G Vs 2 (1 ) 1 2 2(1 ) s p V V 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 26 1 2 2(1 ) s p V V 1. An earthquake warning system is a system of accelerometers, communication, computers, and alarms that is devised for regional notification of a substantial earthquake while it is in progress. 2. This is not the same as earthquake prediction, which is currently incapable of producing decisive event warnings. 3. Several seconds alarm before earthquake attack. Earthquake Warning System 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 27 1 2 2(1 ) s p V Eq. V Early Warning Earthquake Records Displacement Time History Velocity Time History Acceleration Time History--- three features: Peak Ground Acceleration (PGA) Frequency spectrum Duration Time 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 29 The duration time of the El Centro earthquake is 53.73s, with the PGA 341.7 in North-South, 210.1 in East-West, and 206.3 in vertical direction. The site classification is almost II-III. The earthquake magnitude is 6.7 degree with the epicenter distance is 11.5km. Elcentro -0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0 10 20 30 40 50 60 Elcentro 0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 0.0014 0.0016 0.0018 0.0020 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 Acceleration history Power spectral density •EL Centro (US earthquake record) 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 30
2015/9/16 -Shanghai Artificial Wave(SHW2)(上海人工波) .SHW2 is one of the Shanghai artificial wa n of a 005.The. (a)Soft soil (b)Hard soil 1.3Magnitude and Intensity Richter Magnitude .To understand the definition of"magnitude" A Richter Magnitude Scale is and"intensity" .To know the Richter Magnitude and Modified Mercalli Intensity (MMI) M2=1ogA-1og4,=10g(4/4,) MMI scale 出sw 肉大子 Magnitude(in China) Magnitude M,=logA,+R(△) ■Magnit恤eethereleased at the =log Ap+log Vo(T)-log 4-3 M=(A/T)+o(△)+C Mp=log(A/T)+Q+S logE=11.8+1.5M 6
2015/9/16 6 SHW2 is one of the Shanghai artificial waves, which designed for the constructions in Shanghai, according to the Code for Seismic Design of Buildings (GB50011). It imitates the seismic waves for the site classification IV in Shanghai. The damping ratio is 0.05. The PGA is 35.0 . SHW2 -0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0 5 10 15 20 25 30 35 40 SHW2 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 Acceleration history Power spectral density •Shanghai ArtificialWave (SHW2)（上海人工波） 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 31 Power Spectrum of different soil (功率谱) 10 20 30 40 50 0 0 10 2 4 6 8 20 30 40 50 60 (Hz) (rad/s) (cm /s ) 2 6 12 18 24 30 0 0 10 2 4 6 8 20 30 40 50 60 (Hz) (rad/s) 2 (cm /s ) 2 2 (a) Soft soil (b) Hard soil 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 32 1.3 Magnitude and Intensity To understand the definition of “magnitude” and “intensity” To know the Richter Magnitude and Modified Mercalli Intensity (MMI) To evaluate earthquake intensity by using MMI scale 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 33 A Richter Magnitude Scale is a base-10 logarithmic scale obtained by calculating the logarithm of the amplitude (振幅) of earthquake wave measured by a seismograph . Q4: Base on this formula, how many times for an earthquake amplitude of wave increase, when the magnitude scale increase 1? (Tips: log10=1) Richter Magnitude log log = log( / ) M A A A A L 0 0 Elcentro -0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0 10 20 30 40 50 60 The Richter Magnitude Scale (abbreviated RMS, denoted as ML ) 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 34 Magnitude (in China) P P 0 0 log +R = log +log V ( ) log M A L A T A 3 B M A Q S log( / T)+ + M A T S ( / )+ +C ML,MS ,MB：Magnitude obtained from Near Earthquake, Surface Wave and Body Wave T ：Period corresponding to A or V, σ(Δ) , Q: started calculation function , C,S: Adjusted value of seismic station. 2015/9/16 熊海贝 同济大学 xionghaibei@tongji.edu.cn 35 Magnitude measures the energy released at the source of the earthquake. Magnitude is determined from measurements on seismographs(地震仪) . Magnitude log E 11.8 1.5M Example: If M increase 1, how about the energy increase? tips: the log E=1.5, it means E = 101.5 = 31.6 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 36
2015/9/16 Magnitude classification: Intensity Micro/minor earthquakes: <3.9 moderate earthquakes: 4长<59 ed by the earth 6KM<6.9 。Grem,earthquakes 7<k9.9 people's reaction to the shaking 10 (never recorded) observation of other plrysical effects. Intensity Scale Modified Mercalli Intensity (MMI) 色 ()cale Modified Mercalli Intensity (MMI) Modified Mercalli Intensity (MMI) VI Strong Feltby al 7
2015/9/16 7 Magnitude classification: • Micro/minor earthquakes: M10 (never recorded) 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 37 Intensity measures the strength of shaking produced by the earthquake at a certain location. Earthquake intensity are based on: • people’s reaction to the shaking • observed damage to structures and ground surface • observation of other physical effects. Intensity 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 38 39 • A 12-degree Modified Mercalli Intensity (MMI) proposed by H. O. Wood and Frank Neumann (1931) is widely adopted in North American and other parts of the world. • In China, 12-degree intensity scales as similar as MMI are adopted and issued in 2008. • Other 12-degree Medvedev-Sponheuer-Karnik (MSK) Scale (1964) in Europe and the 7-degree scale of the Japanese Meteorological Agency (JMA). Intensity Scale 1884, Rossi-Forel scale,10-degree, 1906, Giuseppe Mercalli revised the 10-degree Mercalli Intensity . 1902, Adolfo Cancani and August Heinrich Sieberg expented 10 to 12 degree. 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 39 40 I Instrumental. Not felt . Ⅱ Weak. Felt only by a few persons Ⅲ Slight. Felt quite noticeably indoors Ⅳ Moderate. felt indoors by many, outdoors by a few Modified Mercalli Intensity (MMI) 41 Ⅴ Rather Strong. Felt by nearly everyone Modified Mercalli Intensity (MMI) Ⅵ Strong. Felt by all, buildings cracks Ⅶ Very Strong. Everybody runs outdoors Ⅷ Destructive Partial collapse 42 Ⅸ Violent. Buildings shifted off foundations Modified Mercalli Intensity (MMI) ⅩIntense Some well-built wooden structures destroyed Ⅺ Extreme. Landslides, cracks and deformation of the ground Ⅻ Catastrophic Total destruction
2015/9/16 Modified Mercalli Intensity(MMI) In他raep的av间wndc 亚dsSn品 ys broken.N IX violent a5ms nship between earthqu Magnitude 10-30 40-49 0-m 4.0-4.9 IV-V 50-59 vi-vI 60-69 vI-vm 70+
2015/9/16 8 Ⅰ Instrumental. Not felt except by a very few under especially favorable circumstances. Ⅱ Weak. Felt only by a few persons at rest, especially on upper floors of buildings. Delicately suspended objects may swing. Ⅲ Slight. Felt quite noticeably indoors, especially on upper floors or buildings, but many people do not recognize it as an earthquake. Ⅳ Moderate. During the day felt indoors by many, outdoors by few. At night some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably. Modified Mercalli Intensity (MMI) 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 43 Ⅴ Rather Strong. Felt by nearly everyone, many awakened. Some dishes, windows, etc., broken; a few instances of cracked plaster; unstable objects overturned. Disturbances of trees, poles, and other tall objects sometimes noticed. Ⅵ Strong. Felt by all, many frightened and run outdoors. Some heavy furniture moved; a few instances of fallen plaster or damaged chimneys. Damage slight. Ⅶ Very Strong Everybody runs outdoors. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable in poorly built or badly designed structures; some chimneys broken. Noticed by persons driving motor cars. 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 44 Ⅸ Violent Damage considerable in specially designed structures; well designed frame structures thrown out of plumb; great in substantial buildings, with partial collapse. Buildings shifted off foundations. Ground cracked conspicuously. Underground pipes broken. Ⅷ Destructive. Damage slight in specially designed structures; considerable in ordinary substantial buildings, with partial collapse; great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, and walls. Heavy furniture overturned. Sand and mud ejected in small amounts. Changes in well water. Persons driving motor cars disturbed. 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 45 Ⅺ Extreme. Few, if any, masonry structures remain standing. Bridges destroyed. Numerous landslides, cracks and deformation of the ground. Ⅻ Catastrophic Total destruction – Everything is destroyed. Lines of sight and level distorted. Objects thrown into the air. The ground moves in waves or ripples. Large amounts of rock move position. Landscape altered, or levelled by several meters. In some cases, even the routes of rivers are changed. ⅩIntense Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations; ground badly cracked. Rails bent. Landslide, Water splashed (slopped) over banks. 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 46 Q5 What is the relationship between earthquake Magnitude and Intensity? Magnitude Typical Maximum MMI 1.0 – 3.0 I 4.0 – 4.9 II – III 4.0 – 4.9 IV –V 5.0 – 5.9 VI –VII 6.0 – 6.9 VII –VIII 7.0+ IX or higher 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 47 Q6: According to MMI scale, could you give us an evaluation of earthquake intensities of Dujiangyan and Shanghai coursed by Wenchuan Earthquake (2008.5.12). Date May 12, 2008) Magnitude 7.98 Ms [1]/7.9 Mw [2] Depth 19 kilometres (12 mi) Epicenter 31°01′16″N 103°22′01″ E31.021°N 103.367°E (Yingxiu, Wenchuan, in Sichuan Province) Max. intensity XI MM/CSIS[3][4] Casualties 69,195 dead[6] 18,392 missing[6][7] 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 48
2015/9/16 Magnitude Intensity Thank you! Different characteristics of earthquakes. Magnitude measures the energy releused at the source of the earthquake.Magnitude is determined Homework: from measurements on seismographs. Review Chapter I Intensity measures the strength of shaking produced by the earthquake at a certain location.Intensity is n每 Register to website determined from effects on people,human structures. and the natural environment. 9
2015/9/16 9 Different characteristics of earthquakes. Magnitude measures the energy released at the source of the earthquake. Magnitude is determined from measurements on seismographs. Intensity measures the strength of shaking produced by the earthquake at a certain location. Intensity is determined from effects on people, human structures, and the natural environment. Magnitude / Intensity 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 49 Thank you! Homework: Review Chapter 1 Register to website 2015/9/16 Haibei XIONG College of Civil Engineering, Tongji University 50