The magnitude 7.3 (Ms) El Asnam earthquake, in Algeria, was probably the first thrust seismic event with so detailed descriptions of the surface breaks. Main and secondary surface ruptures, and scarps created by the earthquake, were finely described by several geologists, among which I selected the 1983 Tectonics paper by Hervé Philip (one of my teachers when I was student in Montpellier in the eighties) and Mustafa Meghraoui. The 3D sketches below come from this famous paper.
Few years later, the same authors (plus Francis Albarède and Armando Cisternas) published in BSSA results of some of the first trenching ever mader across reverse faults. They identified the 1980 rupture in section as well as two older earthquake events in the past 7000 years.
The sketch below shows the three increments of slip (earthquakes), the last one being the 1980 rupture.
The trench illustrated above is labeled II on the 3D sketch below. It is across the most frontal thrust, SE of the growing anticline.
- Philip, H., & Meghraoui, M. (1983). Structural analysis and interpretation of the surface deformations of the El Asnam earthquake of October 10, 1980. Tectonics, 2(1), 17-49.
- Meghraoui, M., Philip, H., Albarede, F., & Cisternas, A. (1988). Trench investigations through the trace of the 1980 El Asnam thrust fault: Evidence for paleoseismicity. Bulletin of the Seismological Society of America, 78(2), 979-999.
