圣安德烈亚斯断层（San Andreas fault）北部有数百千米长的破裂（图2）。VII到IX地震烈度与地表同震断裂长度平行，在陆地达到80千米（图3 – 图6）图。地表地震烈度与地下地质条件有清楚的关联。沉积物谷地比附近基岩地区遭受更强烈的振动。旧金山湾区填海造地区的振动最大。
这场地震所造成的很大水平位移和巨大的破裂长度困惑了当时的地质学家们。在当时，人们对断层重要性和断层积累变形的认知不足。加州地震调查委员会调查和分析了这场大地震，在1908年发表了著名的“地震力学”报告（A.C. Lawson, The Mechanics of the Earthquake, The California Earthquake of April 18, 1906, Report of the State Earthquake Investigation Commission, Vol.1, Parts I and II, Carnegie Institution of Washington,Washington, D.C., USA. 1908, p. 451）（图7）。这份调查报告主要集中在旧金山大地震的地震波、断裂和大地形变三个方面。之后，H. F. Reid教授在1910年提出了他的地震震源弹性回跳理论（H.F. Reid, The Mechanics of the Earthquake, The California Earthquake of April 18, 1906, Report of the State Earthquake Investigation Commission, Vol.2, Carnegie Institution of Washington, Washington, D.C., USA.1910, p. 192）（图7）。
例如，H. F. Reid教授在报告中指出地震的做功和能量是：“This energy was stored up in the rock as potential energy of elastic strain immediately before the rupture; when the rupture occurred, it was transformed into the kinetic energy of the moving mass, into heat and into energy of vibrations; the first was soon changed into the other two. When we consider the enormous amount of potential energy suddenly set free, we are not surprised, that, in spite of the large quantity of heat which must have been developt on the fault-plane, an amount was transferred into elastic vibrations large enoughto accomplish the great damage resulting from the earthquake and to shake the whole world so that seismographs, almost at the antipodes, recorded the shock.” 孕存在断裂两侧变形岩石中的弹性变形能是造成地震的能量。这个地震能量转变成了地震波动能和大量断裂带的热能。因此，这个理论必然导致，地震过程是升温过程。这指导了不少人研究断裂摩擦升温，造成高温矿物与玻璃。可是，人们在地震断裂带就是难以发现任何高温矿物。
