000004765 001__ 4765
000004765 005__ 20200204141850.0
000004765 037__ $$aCTALK-2020-0104
000004765 100__ $$aVan Daele, Maarten
000004765 245__ $$aIntraslab versus megathrust earthquakes: spectral characteristics result in distinct lacustrine deposits
000004765 260__ $$c2019
000004765 269__ $$c2019-04-26
000004765 520__ $$aSubduction zone seismicity arises from megathrust, crustal and intraslab earthquakes,  and  understanding  the  recurrence  patterns  of  each  type  is  crucial  for  hazard  assessments.  Specifically  intraslab  earthquakes  have  recently  proven  to  pose a significant hazard along subduction zones, as evidenced by the destructive September 2017 Chiapas Mw 8.2 (Mexico) earthquake and the recent November 30  2018  Mw  7.0  Anchorage  (Alaska)  earthquake.  Interestingly,  intraslab  earthquakes  have  a  higher-frequency  source  spectrum  then  megathrust  earthquakes  as  a  result  of  the  higher  stress  drop  for  a  given  magnitude.  Here  we  compare  acceleration  response  spectra  of  recent  and  historical  intraslab  and  megathrust  earthquakes along a longitudinal profile in central Chile and show that this difference  in  source  frequency  spectrum  increases  when  moving  land  inward  (e.g., towards  the  Andes  in  South  America).  We  further  illustrate  how  these  differ-ent  response  spectra  provide  an  opportunity  for  lacustrine  paleoseismology,  as  higher-frequency  accelerations  from  intraslab  earthquakes  are  hardly  attenu-ated  in  rocks  of  a  lake’s  watershed,  whereas  lower-frequency  accelerations  from  megathrust earthquakes are amplified in soft lake sediments. We indeed observe this in Lo Encañado Lake, located in the central Chilean Andes, where megathrust  earthquakes  merely  trigger  subaquatic  (soft  sediment)  slope  failures,  while  intraslab earthquakes also trigger subaerial rock slides/avalanches, resulting in an additional  postseismic  turbidite  in  the  lake.  We  conclude  that  lakes  may  be  the  only  geological  archives  that  hold  intraslab  paleoseismic  records,  and  that  lakes  in other subduction zones (e.g., Cascadia) may hold similar records. Combining this  kind  of  lacustrine  records  with  coastal  and  deep-marine  paleoseismology  will  permit  the  construction  of  recurrence  models  for  the  different  seismogenic  sources, and to evaluate the temporal correlations among them, thereby improving hazard assessments.
000004765 594__ $$aNO
000004765 700__ $$aVanneste, Kris
000004765 700__ $$aMoernaut, Jasper
000004765 700__ $$aAraya-Cornejo, Cristian
000004765 700__ $$aPille, Thomas
000004765 700__ $$aSchmidt, Sabine
000004765 700__ $$aKempf, Philipp
000004765 700__ $$aMeyer, Inka
000004765 700__ $$aCisternas, Marco
000004765 773__ $$tSeismological Society of America Annual Meeting 20019, Seattle, USA
000004765 8560_ $$fkris.vanneste@observatoire.be
000004765 906__ $$aContributed
000004765 980__ $$aCTALKCONT