TY  - JOUR
A1  - Schöpa, Anne
A1  - Chao, Wei-An
A1  - Lipovsky, Bradley P.
A1  - Hovius, Niels
A1  - White, Robert S.
A1  - Green, Robert G.
A1  - Turowski, Jens M.
T1  - Dynamics of the Askja caldera July 2014 landslide, Iceland, from seismic signal analysis
BT  - precursor, motion and aftermath
JF  - Earth surface dynamics
N2  - Landslide hazard motivates the need for a deeper understanding of the events that occur before, during, and after catastrophic slope failures. Due to the destructive nature of such events, in situ observation is often difficult or impossible. Here, we use data from a network of 58 seismic stations to characterise a large landslide at the Askja caldera, Iceland, on 21 July 2014. High data quality and extensive network coverage allow us to analyse both long- and short-period signals associated with the landslide, and thereby obtain information about its triggering, initiation, timing, and propagation. At long periods, a landslide force history inversion shows that the Askja landslide was a single, large event starting at the SE corner of the caldera lake at 23:24:05 UTC and propagating to the NW in the following 2 min The bulk sliding mass was 7-16 x 10(10) kg, equivalent to a collapsed volume of 35-80 x 10(6) m(3). The sliding mass was displaced downslope by 1260 +/- 250 m. At short periods, a seismic tremor was observed for 30 min before the landslide. The tremor is approximately harmonic with a fundamental frequency of 2.3 Hz and shows time-dependent changes of its frequency content. We attribute the seismic tremor to stick-slip motion along the landslide failure plane. Accelerating motion leading up to the catastrophic slope failure culminated in an aseismic quiescent period for 2 min before the landslide. We propose that precursory seismic signals may be useful in landslide early-warning systems. The 8 h after the main landslide failure are characterised by smaller slope failures originating from the destabilised caldera wall decaying in frequency and magnitude. We introduce the term "afterslides" for this subsequent, declining slope activity after a large landslide.
Y1  - 2018
U6  - https://doi.org/10.5194/esurf-6-467-2018
SN  - 2196-6311
SN  - 2196-632X
VL  - 6
IS  - 2
SP  - 467
EP  - 485
PB  - Copernicus
CY  - Göttingen
ER  -