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 movement2015/9/16 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 up￾and-down and side-to￾side 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