Soft-sediment deformation structures are often used as evidence for paleo-earthquakes. When several deformed horizons are present, one has to ask whether repeated slope failure at the sediment surface has built-up the stratigraphic record. Another option would be that a single failure event could have concurrently created surficial and sub-surface deformed horizons at different stratigraphic levels. The implications of these differing models are important for the timing of palaeo-earthquakes. In a new paper, Alsop et al. used the late Pleistocene Lisan Formation from the Dead Sea Basin to catalogue and establish key criteria that help distinguish surface versus sub-surface intrastratal deformation of soft-sediments. The paper is available for free for 50 days!more
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2021-12-27 | in Paper
2017-12-04 | in Paper | 6 responses
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
An interesting summer school will be held near Cologne, Germany, from 21-27 August 2016. The GSGS Summer School on Dates and Rates of Change in the Quaternary is devoted to teach all different kinds of Quaternary dating methods such as Ar/Ar, cosmogenic nuclides, luminescence, palaeolimnology, palaeomagnetism, radiocarbon and tephrochronology. It is designed for PhD students, postdoctoral researchers and advanced master’s students in geosciences and will be held in English. Deadline for application is 10 June. The workshop is free for all accepted participants. The summer school is funded through the Institutional Strategy of the University of Cologne and supported by the Geoverbund ABC/J. That’s a great opportunity, make sure to apply before it’s too late!
Thanks to Silke for spreading the news.
3He dating of rockfalls helps to distinguish between proximal and distal paleo-earthquakes in Christchurch, NZ2014-10-13 | in Earthquake
The 2011 Christchurch earthquake series had severe consequences and surprised scientists for many reasons. Ground motions were extremely strong despite the relative moderate magnitudes of the quakes (MW 5.3-7.1). The events happened on a system of hitherto unknown faults, some of which are located directly below Christchurch. Earthquake environmental effects (EEE), especially liquefaction, were intense and widespread. It turned out that subsequent quakes reactivated the same feeder dikes of sand blows, showing that saturated sediments are susceptible of liquefaction no matter if they had been liquefied recently (also see the paper of Quigley et al. (2013) on the liquefaction effects). Another stunning lesson was the occurrence of intense rockfall in the vicinity of Christchurch. In a recently published study, Mackey and Quigley (2014) dated rockfall boulders with 3He and show that they allow to estimate the recurrence intervall of local seismic events like the 2011 series. This works is a very interesting way to use EEE for paleo-earthquake studies. more