TY - JOUR
T1 - Distinguishing intraplate from megathrust earthquakes using lacustrine turbidites
AU - Daele, Maarten Van
AU - Araya-Cornejo, Cristian
AU - Pille, Thomas
AU - Vanneste, Kris
AU - Moernaut, Jasper
AU - Schmidt, Sabine
AU - Kempf, Philipp
AU - Meyer, Inka
AU - Cisternas, Marco
N1 - Funding Information:
Van Daele acknowledges financial support from the Research Foundation–Flanders (FWO). Araya-Cornejo, Moernaut, and Cisternas were funded by the Chilean FONDECYT project 1190258; Cisternas was also funded by the Millennium Nucleus CYCLO–Millennium Scientific Initiative (NC160025), and Moernaut by theAustrian Science Fund (FWF) (project P30285-N34). We thank S. Barrientos and R. Urrutia for facilitating fieldwork, and W. Vandoorne, A. Peña, and P. Guzmán for help in the field. R. Achten is acknowledged for use of the CT scanner. We thank L. Leithold, C. Goldfinger, J. Howarth, and an anonymous reviewer for constructive reviews of an earlier version of this manuscript.
Publisher Copyright:
© 2019 Geological Society of America.
PY - 2019
Y1 - 2019
N2 - Subduction zone seismicity arises from megathrust, crustal, and intraslab earthquakes, and understanding the recurrence patterns of each type is crucial for hazard assessments. Lake sediments can record earthquakes from all three seismogenic sources. Here, we studied the turbidite record of Lo Encañado, an Andean lake located in central Chile. We show that Lo Encañado turbidites can be attributed to (1) subaquatic slope failure by earthquake shaking (coseismic phase), (2) floods or human impact, and (3) postseismic catchment response. All historical events with shaking intensities > VI (modified Mercalli intensity) have triggered coseismic turbidites, but only the intraplate earthquakes triggered subaerial slope failures followed by postseismic turbidites. We argue that this contrasting result is due to different spectra of seismic waves from these earthquake sources: higher-frequency accelerations from intraplate earthquakes are hardly attenuated in rocks around the lake, whereas lowerfrequency accelerations from megathrust earthquakes are amplified in soft lake sediments. We tested our findings by comparing acceleration response spectra of recent and historical intraslab and megathrust earthquakes along a longitudinal profile. Results suggest that the location of Andean lakes is ideal to distinguish earthquake sources.
AB - Subduction zone seismicity arises from megathrust, crustal, and intraslab earthquakes, and understanding the recurrence patterns of each type is crucial for hazard assessments. Lake sediments can record earthquakes from all three seismogenic sources. Here, we studied the turbidite record of Lo Encañado, an Andean lake located in central Chile. We show that Lo Encañado turbidites can be attributed to (1) subaquatic slope failure by earthquake shaking (coseismic phase), (2) floods or human impact, and (3) postseismic catchment response. All historical events with shaking intensities > VI (modified Mercalli intensity) have triggered coseismic turbidites, but only the intraplate earthquakes triggered subaerial slope failures followed by postseismic turbidites. We argue that this contrasting result is due to different spectra of seismic waves from these earthquake sources: higher-frequency accelerations from intraplate earthquakes are hardly attenuated in rocks around the lake, whereas lowerfrequency accelerations from megathrust earthquakes are amplified in soft lake sediments. We tested our findings by comparing acceleration response spectra of recent and historical intraslab and megathrust earthquakes along a longitudinal profile. Results suggest that the location of Andean lakes is ideal to distinguish earthquake sources.
UR - http://www.scopus.com/inward/record.url?scp=85060492007&partnerID=8YFLogxK
U2 - 10.1130/G45662.1
DO - 10.1130/G45662.1
M3 - Article
AN - SCOPUS:85060492007
VL - 47
SP - 127
EP - 130
JO - Geology
JF - Geology
SN - 0091-7613
IS - 2
ER -