The Bolivian Amazon is a vast plain with almost zero topography. It hosts a huge and dynamic river system on the east side of the Andes. So far, little was known about the active tectonics of the area. In a new paper, Umberto Lombardo and I show that there are active faults parallel to the Andes, and also perpendicular to the mountain front. We used the TanDEM-X DEM and geomorphological analyses of the fluvial system to investigate the faults and their impact on river dynamics. We show that in such a low-relief setting, dip-slip earthquakes can catastrophically change river courses. If you don’t have the time to read the full paper, here’s a short summary.
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The Tien Shan takes up about 20 mm/yr of N-S shortening as a result of the India-Eurasia convergence. Recent paleoseismological studies have shown that the shortening is accommodated by a large number of faults, whose slip rates are relatively low. Although the historical earthquake catalogues only reach back a few hundred years, we know that the Tien Shan has seen some of the strongest intracontinetal quakes world-wide with magnitudes exceeding M8. Paleoseismological studies have revealed a large number of surface-rupturing earthquakes, too. But the question is: Do all these known faults rupture in strong earthquakes? In a recent paper, my colleagues and I argue that there is at least one major fault in the Northern Tien Shan that is creeping (Mackenzie et al., 2018). more
Almaty, the former capital of Kazakhstan and home to ~2 million people, is a rapidly growing, vibrant city, beautifully situated at the foothills of the mighty Zailisky Alatau, the northernmost mountain range of the Tien Shan at this longitude. The city sits on a huge alluvial fan with the snow-capped mountains in the background, reaching 5,000 m elevation. Almaty has suffered from earthquakes in its young history: in 1887, the Verny earthquake with a magnitude of about 7.3 had its epicentre a few kilometres west of the city but did not produce surface ruptures (Verny is the old name of Almaty). Only two years later, the M8 Chilik earthquake ruptured the surface 100 km to the southeast of Almaty. Finally, Almaty was heavily damaged by the 1911 Chon Kemin earthquake with a magnitude of ~8, which occurred on the southern flank of the Zailisky Alatau. In our new paper we now report on a fault that did not rupture in historical times, but surely did so in the Holocene – and this fault is right beneath the city. more
Several new papers deal with paleoseismology and active tectonics studies. Wiatr et al. used terrestrial LiDAR to analyse limestone bedrock scarps, Hornblow et al. investigated the Darfield earthquake source in NZ. Sarikaya et al. present new data on offset alluvial fans in Central Turkey; Xu et al. present geological data on two historical seismic events in Tibet. Tectonic morphology is used by Barcelona et al. in NW Argentina. Mathew et al. use remote sensing data to analyze coseismic deformation in China. Ed Garrett and colleagues present data on 1000 years of megathrust quakes in Chile, and Bemis et al. have an interesting article on UAVs and paleoseismology. more
A new paper in Tectonophysics deals with the use of terrestrial LiDAR for identifying the slip vectors on fault planes. Thomas Wiatr, Klaus Reicherter, Ioannis Papanikolaou, Tomás Fernandez-Steeger and Jack Mason collected and processed data from Crete island (Greece), where they scanned the scarp of the Spili Fault. They imaged numerous kinematic (slip direction) indicators like slickensides with this relatively new technique. The t-LiDAR data were then compared to traditional compass measurements in order to get an idea about the derivation betwen old-school measurements and high-tech methods. more
