Observation of a Synchronicity between Shallow and Deep Seismic Activities during the Foreshock Crisis Preceding the Iquique Megathrust Earthquake





We analyze at a broad spatial scale the slab seismicity during one of the longest and best recorded foreshock sequence of a subduction earthquake to date: the M8.1 2014 Iquique earthquake in Chile.  We observe the synchronisation of this sequence with seismic events occurring in the deep slab (depth ~100km). This synchronisation supports the existence of long-range seismic bursts already observed in the Japan Trench subduction. It suggests that, like for the 2011 Tohoku earthquake, the deep slab was involved in the nucleation process of the Iquique earthquake.  We interpret these observations by the presence of pressure pulses propagating in transient fluid channels linking the deep slab where dehydration occurs to the shallow seismogenic zone before the earthquake. These observations may seem surprising but they are in line with the short-lived pulse-like channelized water escape from the dehydration zone predicted by recent studies in slab mineralogy and geochemistry.


Abers, G., Nakajima, J., Keken, P., Kita, S., & Hacker, B. (2013). Thermal-petrological controls on the location of earthquakes within subducting plates. Earth Plan. Sc. Lett, 369, 178–187.

Aden-Antoniow, F., Satriano, C., Bernard, P., Poiata, N., Aissaoui, E., Vilotte, J., & Frank, W. (2020). Statistical analysis of the preparatory phase of the M8.1 Iquique earthquake, Chile. J. Geophys. Res, 2019JB019337.

Angiboust, S., Pettke, T., Hoog, J., Caron, B., & Oncken, O. (2014). Channelized fluid flow and eclogite-facies metasomatism along the subduction shear zone. J. Petrol, 55, 883–916.

Bedford, J., Moreno, M., Schurr, B., Bartsch, M., & Oncken, O. (2015). Investigating the final seismic swarm before the Iquique-Pisagua 2014 Mw 8.1 by comparison of continuous GPS and seismic foreshock data. Geophys. Res. Lett, 42, 3820–3828.

Bedford, J. (2020). Months-long thousand-kilometre-scale wobbling before great subduction earthquakes. Nature, 580, 628–635.

Beroza, G., & Ide, S. (2011). Slow earthquakes and nonvolcanic tremors. Annu. Rev. Earth Planet. Sci, 39, 271–296.

Bouchon, M. (2016). Potential slab deformation and plunge prior to the Tohoku, Iquique and Maule earthquakes. Nature Geosci, 9, 380–383.

Bouchon, M. (2022). Observation of rapid long-range seismic bursts in the Japan Trench subduction leading to the nucleation of the Tohoku earthquake. Earth Plan. Sc. Lett, 594, 117696.

Boudin, F. (2021). Slow slip events precursory to the 2014 Iquique earthquake, revisited with long-base tilt and GPS records. Geophys. J. Int, 228, 2092–2121.

Bouih, M., Panet, I., Remy, D., Longuevergne, L., & Bonvalot, S. (2022). Deep mass redistribution prior to the 2010 Mw 8.8 Maule (Chile) Earthquake revealed by GRACE satellite gravity. Earth Plan. Sc. Lett, 584, 117465.

Cabrera, L., Ruiz, S., Poli, P., Contreras-Reyes, E., Osses, A., & Mancini, R. (2021). Northern Chile intermediate-depth earthquakes controlled by plate hydration. Geophys. J. Int, 226, 78–90.

Chlieh, M. (2011). Interseismic coupling and seismic potential along the Central Andes subduction zone. J. Geophys. Res, 116(B12), 1–21.

Contreras-Reyes, E. (2021). Subduction zone fluids and arc magmas conducted by lithospheric deformed regions beneath the central Andes. Scientific Reports, 11(23078).

Cruz-Atienza, V., Villafuerte, C., & Bhat, H. (2018). Rapid tremor migration and pore-pressure waves in subduction. Nature Comm.

Duputel, Z. (2015). The Iquique earthquake sequence of April 2014: Bayesian modeling accounting for prediction uncertainty. Geophys. Res. Lett, 42, 7949–7957.

Edwards, J. (2018). Corrugated megathrust revealed offshore from Costa Rica. Nature Geosci, 11, 197–202.

Ekström, G., Nettles, M., & Dziewonski, A. (2012). The global CMT project 2004-2010: Centroid-moment tensors for 13,017 earthquakes. Phys.Earth Planet. Inter, 200–201.

Ferrand, T. (2017). Dehydration-driven stress transfer triggers intermediate-depth earthquakes. Nature Comm, 8, 15247.

Galbraith, C., Smyth, P., & Stern, H. (2020). Quantifying the association between discrete event time series with applications to digital forensics. J. Roy. Stat. Soc, Series A, 0964–1998 20 183000.

Gasc, J., Hilairet, N., Yu, T., Ferrand, T., Schubnel, A., & Y, W. (2017). Faulting of natural serpentine: Implications for intermediate-depth seismicity. Earth Plan. Sc. Lett, 474, 138–147.

Ghosh, A. (2010). Rapid continuous streaking of tremor in Cascadia. Geoch Geophys. Geosyst, 11, Q12010.

Gomberg, J. (2010). Slow slip phenomena in Cascadia from 2007 and beyond: A review. Geol. Soc. Am. Bull, 122, 963–978.

Green, H., & Houston, H. (1995). The mechanics of deep earthquakes. Ann. Rev. Earth Planet. Sci, 23, 169–213.

Guillot, S., Schwartz, S., Agard, P., Renard, B., & Prigent, C. (2015). Tectonic significance of serpentinites. Tectonophysics, 1–19.

Hacker, B., Peacock, S., Abers, G., & Holloway, S. (2003). Subduction factory 2. Are intermediate-depth earthquakes in subducting slabs linked to metamorphic dehydration reactions?. J. Geophys. Res, 108.

Hayes, G., Wald, D., & Johnson, R. (2012). Slab1.0: A three-dimensional model of global subduction zone geometries. J. Geophys. Res, 117, B01302.

Ide, S. (2010). Striations, duration, migration, and tidal response in deep tremor. Nature, 466, 356–359.

Jara, J., Soquet, A., Marsan, D., & Bouchon, M. (2017). Long-term interactions between intermediate depth and shallow seismicity in North Chile subduction Zone. Geophys. Res. Lett, 44.

Jara, J. (2018). Kinematic study of Iquique 2014 Mw8.1 earthquake; Understanding the segmentation of the seismogenic zone. Earth Plan. Sc. Lett, 503, 131–143.

John, T. (2012). Volcanic arcs fed by rapid pulsed fluid flow through subducting slabs. Nature Geosci, 5, 489–492.

Kao, H., Shan, S., Rogers, G., & Dragert, H. (2007). Migration characteristics of seismic tremors in the northern Cascadia margin. Geophys. Res. Lett, 34, L03304.

Karabulut, H., Bouchon, M., & Schmittbuhl, J. (2022). Synchronization of small scale seismic clusters reveals large scale plate deformation. Earth Planets Space, 74(158).

Kato, A., & Nakagawa, S. (2014). Multiple slow-slip events during a foreshock sequence of the 2014 Iquique, Chile Mw 8.1 earthquake. Geophys. Res. Lett, 41, 5420–5427.

Kato, A., Fukuda, J., Kumazawa, T., & Nakagawa, S. (2016). Accelerated nucleation of the 2014 Iquique, Chile Mw 8.2 earthquake. Nature Sci. Rep, 6, 24792.

Kawakatsu, H., & Watada, S. (2007). Seismic Evidence for Deep-Water Transportation in the Mantle. Science, 316, 1468–1471.

Kawano, S., Katayama, I., & Okazaki, K. (2011). Permeability anisotropy of serpentine and fluid pathways in a subduction zone. Geology, 39, 939–942.

Keken, P., Hacker, B., Syracuse, E., & Abers, G. (2011). Subduction factory: Depth-dependent flux of H2O from subducting slabs worldwide. J. Geophys. Res, 116, B01401.

Keken, P., Kita, S., & Nakajima, J. (2012). Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones. Solid Earth, 3, 355–364.

Kirby, S., Engdahl, R., & Denlinger, R. (1996). Intermediate-depth intraslab earthquakes and arc volcanism as physical expressions of crustal and uppermost mantle metamorphism in subducting slabs. Subduction Top to Bottom, Am. Geophys. Un. Geophys. Monogr, 96, 195–214.

Lay, T., Yue, H., Brodsky, E., & An, C. (2014). The 1 April 2014 Iquique, Chile, Mw 8.1 earthquake rupture sequence. Geophys. Res. Lett, 41, 3818–3825.

Madariaga, R. (1998). Sismicidad de Chile. Fisica de la Tierra, 10, 221–258.

Meng, L., Huang, H., Bürgmann, R., Ampuero, J., & Strader, A. (2015). Dual megathrust behaviors of the 2014 Iquique earthquake sequence. Earth Planet. Sci. Lett, 411, 177–187.

Metois, M., Vigny, C., & Socquet, A. (2016). Interseismic coupling, megathrust earthquakes and seismic swarms along the Chilean subduction zone (38°-18°S. Pure Appl. Geophys, 173, 1431–1449.

Miller, S., Nur, A., & Olgaard, D. (1996). Earthquakes as a coupled shear stress-high pore pressure dynamical system. Geophys. Res. Lett, 23, 197–200.

Miller, S., Zee, W., Olgaard, D., & Connolly, J. (2003). A fluid-pressure feedback model of dehydration reactions: experiments, modelling, and application to subduction zones. Tectonophysics, 370, 241–251.

Panet, I., Bonvalot, S., Narteau, C., Remy, D., & Lemoine, J. (2018). Migrating pattern of deformation prior to the Tohoku-Oki earthquake revealed by GRACE data. Nature Geosci, 11.

Panet, I., Narteau, C., Lemoine, J., Bonvalot, S., & Remy, D. (2022). Detecting preseismic signals in GRACE gravity solutions : Application to the 2011 Mw 9.0 Tohoku earthquake. J. Geophys. Res, 127.

Peacock, S. (1990). Fluid processes in subduction zones. Science, 248, 329–337.

Peng, Z., & Gomberg, J. (2010). An integrated perspective of the continuum between earthquakes and slow-slip phenomena. Nature Geosci, 3, 599–607.

Plümper, O., John, T., Podladchikov, Y., Vrijmoed, J., & Scambelluri, M. (2017). Fluid escape from subduction zones controlled by channel-forming reactive porosity. Nature Geosci, 10, 150–155.

Poli, P., & Prieto, G. (2014). Global and along-strike variations of source duration and scaling for intermediate-depth and deep-focus earthquakes. Geophys. Res. Lett, 41, 8315–8324.

Prieto, G. (2013). Seismic evidence for thermal runaway during intermediate-depth earthquake rupture. Geophys. Res. Lett, 40, 6064–6068.

Raleigh, C., & Paterson, M. (1965). Experimental deformation of serpentinite and its tectonic implications. J. Geophys. Res, 70, 3965–3985.

Rondenay, S., Abers, G., & P.E, K. (2008). Seismic imaging of subduction zone metamorphism. Geology, 36, 275–278.

Rousset, B., Campillo, M., Shapiro, N., Walpersdorf, A., Titkov, N., & Chebrov, D. (2023). The 2013 slab-wide Kamchatka earthquake sequence. Geophys. Res. Lett, 50.

Ruiz, S. (2014). Intense foreshocks and a slow slip event preceded the 2014 Iquique Mw 8.1 earthquake. Science, 345, 1165–1169.

Ruiz, S., & Madariaga, R. (2018). Historical and recent large megathrust earthquakes in Chile. Tectonophysics, 733, 37–56.

Schurr, B. (2014). Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake. Nature, 512, 299–302.

Shapiro, N., Campillo, M., Kaminski, E., Vilotte, J., & Jaupard, C. (2018). Low-frequency earthquakes and pore-pressure transients in subduction zones. Geophys. Res. Lett, 43, 11083–11094.

Shelly, D., Beroza, G., & Ide, S. (2007). Complex evolution of transient slip derived from precise tremor locations in western Shikoku, Japan. Geochem. Geophys. Geosyst, 8, Q10014.

Sibson, R.. (1992). Implications of fault-valve behavior for rupture nucleation and recurrence, Tectonophysics 18,1031–1042.

Sippl, C., Schurr, B., Asch, G., & Kummerow, J. (2018). Catalogue of Earthquake Hypocenters for Northern Chile Compiled from IPOC (plus auxiliary) seismic stations. GFZ Data Services.

Sippl, C., Schurr, B., Asch, G., & Kummerow, K. (2018). Seismicity structure of the northern Chile forearc from >100,000 double-difference relocated hypocenters. J. Geophys. Res. Solid Earth, 123, 4063–4087.

Socquet, A. (2017). An 8 month slow slip event triggers progressive nucleation of the 2014 Chile megathrust. Geophys. Res. Lett, 44.

Soto, H. (2019). Probing the Northern Chile Megathrust with Seismicity: The 2014 M8.1 Iquique Earthquake Sequence. J. Geophys. Res, 124, 12935–12954.

Taetz, S., John, T., Bröcker, M., Spandler, C., & Stracke, A. (2018). Fast intraslab fluid-flow events linked to pulses of high pore fluid pressure at the subducted plate interface. Earth Plan. Sc. Lett, 482, 33–43.

Vigny, C., Rudloff, A., Ruegg, J., Madariaga, R., Campos, J., & Alvarez, M. (2009). Upper plate deformation measured by GPS in the Coquimbo gap. Chile, Phys. Earth planet. Inter, 175, 86–95.

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How to Cite

Bouchon, M., Guillot, S., Marsan, D., Socquet, A., Jara, J., & Renard, F. (2023). Observation of a Synchronicity between Shallow and Deep Seismic Activities during the Foreshock Crisis Preceding the Iquique Megathrust Earthquake. Seismica, 2(2). https://doi.org/10.26443/seismica.v2i2.849