Premium
Earthquake‐induced soft‐sediment deformations and seismically amplified erosion rates recorded in varved sediments of Köyceğiz Lake (SW Turkey)
Author(s) -
Avşar Ulaş,
Jónsson Sigurjón,
Avşar Özgür,
Schmidt Sabine
Publication year - 2016
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2016jb012820
Subject(s) - varve , geology , siliciclastic , sedimentary rock , sediment , sedimentation , landslide , erosion , seismology , geochemistry , sedimentary depositional environment , geomorphology , structural basin
Earthquake‐triggered landslides amplify erosion rates in catchments, i.e., catchment response (CR) to seismic shocks. In addition to historical eyewitness accounts of muddy rivers implying CRs after large earthquakes, several studies have quantitatively reported increased sediment concentrations in rivers after earthquakes. However, only a few paleolimnological studies could detect CRs within lacustrine sedimentary sequences as siliciclastic‐enriched intercalations within background sedimentation. Since siliciclastic‐enriched intercalations can easily be of nonseismic origin, their temporal correlation with nearby earthquakes is crucial to assign a seismic triggering mechanism. In most cases, either uncertainties in dating methods or the lack of recent seismic activity has prevented reliable temporal correlations, making the seismic origin of observed sedimentary events questionable. Here we attempt to remove this question mark by presenting sedimentary traces of CRs in the 370‐year‐long varved sequence of Köyceğiz Lake (SW Turkey) that we compare with estimated peak ground acceleration (PGA) values of several nearby earthquakes. We find that earthquakes exceeding estimated PGA values of ~20 cm/s 2 can induce soft‐sediment deformations, while CRs seem only to be triggered by PGA levels higher than 70 cm/s 2 . In Köyceğiz Lake, CRs produce Cr‐ and Ni‐enriched sedimentation due to the seismically mobilized soils derived from ultramafic rocks in the catchment. Given the varve chronology, the residence time of the seismically mobilized material in the catchment is determined to be 5 to 10 years.