珠江三角洲构造应力场的光弹模拟

由光弹模拟实验得到的珠江三角洲及邻区的构造应力场反映出：①几乎所有断裂都呈压剪性应力状态，其端点、闭锁点都是应力集中点，应力集中系数为７—９。②部分ＮＷ向断裂的浅部呈张性应变状态，可发生张性破裂并引起４．５级以下的地震。③以１９６２年河源６．１级地震发生时的应力状态为标准考查现今应力场后发现，本区处于无大震的稳定状态，但河源若再发生５．９级以上地震，则意味着外场力增大并超过１９６２年的水平，区内ＮＷ和ＮＥＥ向断裂均有发生６级以上地震的可能。

Photoelastic Simulation for Structural Field of Stress in Pearl River Delta

The photoelastic simulation experiments on the structural field of stress in the PearlRiver delta and the area around have reflected that: 1 ) Almost all the falllts show pressureshearing stress state, the tips and lock spots are stress concentrated points at concentrationcoefficient 7-9; 2) The shallow portions of some of the NW-oriented faults show tensilestrain state, where tensile cracks may occur which may initiate earthquakes at weaker than4. 5 magnitude on Richter scale; 3) Taking the stress state happened during the magnitude6. 1 quake at Heyuan in 1962 as a basis, a sllrvey on the present field of stress shows thatthe region is in a steady state without strong earthquakes. However, put the case that anearthquake stronger than magnitude 5. 9 happens again in the heyuan area, then it signifiesthat the external force has upgraded to one stronger than that of the level in 1962, and theNW-/NEE-oriented faults in the region might possibly bring about quakes stronger thanmagnitude 6.