Forearc deformation across time scales - a tale of fluids, locking and transients

Transcription

1 Forearc deformation across time scales - a tale of fluids, locking and transients Modified from Scholz, 1998; Bilek & Lay, 2002; and Schwartz & Rokosky, 2007 Onno Oncken, GFZ Potsdam with M. Moreno, P. Victor, B. Schurr, I. Ioannidi, J. Bedford, V. Mouslopoulou, I. Urrutia, M. Rosenau, F. Hoffmann, S. Angiboust, S. Li and many more

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3 Topographic architecture of the Chile plate margin tectonically erosive north accretionary south external ridge Coastal Cordillera external ridge Coastal Cordillera

4 Experimental seismotectonic deformation ( years) Elastic strain level 4 Earthquake magnitude time series co-/postseismic coastline interseismic Time (1/10s) Rosenau & Oncken, JGR, 2009

5 The Mw = 7.8, Tocopilla earthquake, aftershocks at updip end of locking drive uplift Schurr et al Fuenzalida et al. 2012

6 Arauco peninsula - Kinematics since c.3 Ma Average uplift rate: 2.3 mm/a coseismic motion Average uplift rate: mm/a Moreno et al, 2010 Bookhagen et al., Melnick et al, 2006, 2009

7 Correlation slope-locking Slope gradient Locking Kinematic locking appears stable 1943 over multiple seismic cycles! Urrutia et al, in prep.

8 0 Are locked patches stable over years? And through what mechanism? Mw8.1 Iquique earthquake, locked Schurr et al., Nature, 2014

9 Slip reversal on upper plate faults during megathrust seismic cycle? Shirzaei et al., GRL, 2012 Coulomb stress change of several 10 kpa only!!

10 extension during postseismic relaxation and afterslip, shortening interseismically? Plio-Quarternary gravels

11 Late interseismic kinematic mode indeed governed by compression landward of the locked zone data in Hoffmann et al., 2018; strain calculation courtesy of S. Lamb

12 Crete Strandlines mark sea level and past earthquakes co-/postseismic coast line northern Chile interseismic southern Chile

13 Chile Crete integration time (kyrs) Mouslopoulou et al., 2015, 2016 Long-term uplift transients in forearcs from earthquake clustering

14 (Moreno et al. EPSL 2012) Preseismic locking and coseismic slip the 8.8. Maule earthquake of coseismic displacement locking and slip preseismic displacement Moreno, Rosenau & Oncken, Nature 2010

15 Seismological image reveals hydraulic transients - the North Chilean case Composite section of ANCORP and CINCA; Oncken et al., 2003; Husen & Kissling, 2001 West Fissure Fault Zone Tocopilla 2007 after before Antofagasta 1995 earthquake Nipress & Rietbrock, 2006

16 Background seismicity and Vp/Vs ratio show correlation with geodetic locking Valdivia rupture zone 2010 Maule rupture zone Moreno et al., 2014 Haberland et al. 2009

17 Pore pressure controls locking? Moreno et al., Nature Geoscience 2014 λ b 0.90 to 1.00 µ eff on plate interface 0.05

18 Strength constraints for forearc faulting complete rupture Li et al., 2014 Domains A B C partial rupture complete rupture

19 Fault healing and relocking after the Maule 2010 earthquake within 1 year Bedford et al pre-maule interseismic loading

20 Postseismic locking recovers at maximum slip domain the Mw 9.5 Chile earthquake of Moreno et al., 2009; Moreno et al,

21 Duration (s) The plate interface is extremely weak and has transient strength evolution, all due to hydraulic system and its transients? Faults may creep or break and they respond to very small stress changes, but what makes them respond to stress changes of just a few 10s kpa? Conclusions and questions Mill yrs Energy release time const. Andean orogeny shortening bursts M o t Locking and asperities at interface appear stable and control localization of upper plate deformation, but over which time scales and is it always the hydraulic system and its variability? kyrs 1 year earthquake clusters on fault networks Upper plate deformation and faulting occurs in?cyclic mode driven by megathrust cycle, but how well synchronized and why do faults break in earthquake clusters? 1 day 1 hour Mw Chile earthquake M o t 3 upper plate response may be compressional or extensional postseismically, dependent on ratio of slip/slip-deficit every cycle? Peng & Gomberg Moment (Nm)

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23 What this means. effective coefficient of friction on plate interface 0.05 friction of banana peel 0.07 Awarded with 2014 Ig Nobel Prize PHYSICS PRIZE: for measuring the amount of friction between a shoe and a banana skin, and between a banana skin and the floor, when a person steps on a banana skin that's on the floor. REFERENCE: "Frictional Coefficient under Banana Skin," Kiyoshi Mabuchi, Kensei Tanaka, Daichi Uchijima and Rina Sakai, Tribology Online 7, no. 3, 2012, pp plate interfaces are weaker than banana peels!

24 Duration (s) Extending the slow earthquake scaling law Andean orogeny 10 Mill yrs M o t shortening bursts kyrs earthquake clusters on fault networks year Energy release time const. 1 day 1 hour M o t 3 Mw Chile earthquake Peng & Gomberg Moment (Nm)

25 Duration (s) Energy release time const Mill yrs Andean orogeny shortening bursts M o t kyrs earthquake clusters on fault networks year 1 day 1 hour M o t 3 Mw Chile earthquake Peng & Gomberg Moment (Nm)

26 2014 M 8.1

27 Gehobene Küste Maule Erdbeben,

28 M>8 Erdbeben 1751? (Lomnitz, 1970) ~7 m Historische koseismische Hebung 1835 M>8 earthquake m (Darwin, 1851) = 2 mm/a Hebungsrate im 1960 Chile Erdbebengebiet Wellenplatform gehoben 1960 M=9.5 c. 2.5 m

29 Strandlinien auf Santa Maria (Südchile)

30 und vor 58 Jahren Moreno et al., 2009

31 2014 M 8.1 Natural lab Chile

32 Locking, earthquakes and why Chile is a perfect natural lab Scholz, M Moreno et al., in prep. Ipoc-network.org Ipoc-network.org >100 yrs since last event

33 7 months of afterslip and aftershocks the 8.8. Maule earthquake of Slip and locking Daily slip solution Cumulative slip Moreno et al., 2010 Bedford et al., 2013

34 Daily slip solutions reveal two velocity regimes for M8.8., 2010 Maule earthquake 7-month afterslip evolution M o t Afterslippulses slip velocity 9 cm/day M o t 3 Ide, 2007 Moreno, Rosenau & Oncken, Nature 2010 Bedford et al. EPSL, 2013

35 Sick et al., 2006 Controls on subduction erosion: the trench fill Bangs and Cande, 1997 accretion erosion Oncken, in prep. Oncken et al., 2006

36 Duration (s) Der erweiterte Erdbeben-/ Transienten -Zoo Andean orogeny 10 Mill yrs M o t shortening bursts kyrs earthquake clusters on fault networks year Deformationsenergie Zeit konst. 1 day 1 hour M o t 3 Mw Chile earthquake Peng & Gomberg Moment (Nm)

37 Megathrust and upper plate earthquakes cluster? 15 yrs seismicity Moreno et al., 2009; Moreno et al, 2012

38 Arauco Basin: Stop and go inversion & uplift since 3.6 Ma Melnick et al., 2006 GSA-Bull

39 Seismic cycle-related evolution of uplift Bookhagen et al., 2006 Earthquake recurrence ~ 185 yrs

40 M>8 earthquake 1751? (Lomnitz, 1970) ~7 m Historical coseismic uplift 1835 M>8 earthquake m (Darwin, 1851) = 2 mm/a Hebungsrate im 1960 Chile Erdbebengebiet Wave-cut platform upliftet1960 M=9.5 c. 2.5 m

41 Coseismic slip, preseismic locking and coastal uplift Mw8.8 Maule earthquake of (Moreno et al. EPSL 2012) Coseismic slip Coseismic uplift Preseismic locking Pre-Maule water mark

42 Kinematics since c.3 Ma Average uplift rate: 2.3 mm/a Average uplift rate: mm/a Moreno et al, 2010 Bookhagen et al., Melnick et al, 2006, 2009

43 Co- and postseismic deformation of surface from Antofagasta earthquake

44 ??Interseismic shortening at low slip rates

45 Uplifted coast Maule earthquake, Pre-Maule water mark

46 45 years later Moreno et al., 2009

47 Seismic barrier and the geological record and the uncertainty

48 Der Erdbeben-Zoo und die Bananenschale - was wir schon immer über Subduktionszonen wissen wollten Megacities 2015 in mill. inh. Onno Oncken, GFZ Potsdam mit M. Moreno, J. Bedford, M. Rosenau, S. Angiboust, B. Schurr, P. Victor, V. Mouslopoulou

49 Erdbebenaktivität und Vp/Vs Verhältnis korrelieren mit der Kopplung! Valdivia Bruchzone 2010 Maule Bruchzone Moreno et al., 2010 Haberland et al. 2009

50 Depth (km) Stress/fluid pressure fluctuations in transition zone Shear stress (MPa) = 0.4 (~Byerlee s law at hydrostatic pore fluid pressure) = s -1 (convergence velocity) = 0.03 (effective coefficient of friction) strain-rate increase. = 10-4 s -1 (slow earthquakes) At seismic cycle time scale, transition depth depends on (1) Pore fluid pressure and on (2)Strain rate Angiboust et al. 2015; Ioannidi et al., in prep.