Chixoy-Polochic Fault

The Chixoy-Polochic Fault, also known as Cuilco-Chixoy-Polochic Fault, is a major fault zone in Guatemala and southwestern Mexico. It runs in a light arc from the east coast of Guatemala to Chiapas, following the deep valleys of the Polochic River, Chixoy River and Cuilco River.[1]

Extent, slip rate and total displacement

The Chixoy-Polochic Fault is a large, dominantly strike-slip, left-lateral fault that runs largely parallel to the Motagua Fault situated some 80 km to its south. Both fault zones are onshore extensions of the Bartlett Deep, or Cayman Trench of the Caribbean Sea, which marks the tectonic boundary between the Caribbean Plate and the North American Plate.[1] Both faults connect at sea west of the Guatemalan coast. To the west, the Polochic fault may branch onto the Tonala fault of western Chiapas. It does not continue at sea across the Pacific coastal plain and marine shelf.[2]

The Chixoy-Polochic fault has total displacement of 125 km, well constrained by the offset of Paleocene or Eocene laramide folds and thrusts.[3] Fault velocity has been estimated at 4.8 ± 2.3 mm/y over the past 10 ky,[4] 2.5–3.3 mm/y over the last 7–10 Myr,[5] and less than 5 mm/y during the current interseismic cycle.[6]

Seismicity

While recent seismic activity is more prominent in the Motagua fault, some studies suggest the Chixoy-Polochic Fault is still capable of producing major earthquakes. The magnitude of 7.5–7.8 Mw 1816 Guatemala earthquake of western Guatemala has been ascribed to the Polochic Fault,[7] although this has been disputed.[8][9] Most recent recorded fault activity includes at least for slip events between 17 ka and 13 ka BP,[4] and aseismic surface rupture over some of the past 5 centuries.[8] One or several intermediate to large earthquakes between 850 CE and 1,400 CE, including a cluster of 4 earthquakes over 60 years during the Classic Maya collapse.[8] The fault display a 5 km to 10 km deep zone of microseismicity [10] which may represent a locked zone. Only ≤ 5.6 Mw earthquakes have occurred on the fault since the beginning of regional instrumental records (1920 CE).[7]

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References
  1. Ortega-Gutiérrez, Fernando; et al. (2007). "The Maya-Chortís Boundary: A Tectonostratigraphic Approach" (PDF). International Geology Review. 49 (11): 996–1024. Bibcode:2007IGRv...49..996O. doi:10.2747/0020-6814.49.11.996.
  2. Keppie, J. Duncan; Morán-Zenteno, Dante J. (2005-05-01). "Tectonic Implications of Alternative Cenozoic Reconstructions for Southern Mexico and the Chortis Block". International Geology Review. 47 (5): 473–491. Bibcode:2005IGRv...47..473K. doi:10.2747/0020-6814.47.5.473. ISSN 0020-6814.
  3. Burkart, Burke (1978-06-01). "Offset across the Polochic fault of Guatemala and Chiapas, Mexico". Geology. 6 (6): 328. Bibcode:1978Geo.....6..328B. doi:10.1130/0091-7613(1978)6<328:OATPFO>2.0.CO;2. ISSN 0091-7613.
  4. Authemayou, Christine; Brocard, Gilles; Teyssier, Christian; Suski, Barbara; Cosenza, Beatriz; Morán-Ical, Sergio; González-Véliz, Claussen Walther; Aguilar-Hengstenberg, Miguel Angel; Holliger, Klaus (2012-07-01). "Quaternary seismo-tectonic activity of the Polochic Fault, Guatemala" (PDF). Journal of Geophysical Research: Solid Earth. 117 (B7): B07403. Bibcode:2012JGRB..117.7403A. doi:10.1029/2012JB009444. ISSN 2156-2202.
  5. Brocard, Gilles; Teyssier, Christian; Dunlap, Walker James; Authemayou, Christine; Simon-Labric, Thibaud; Cacao-Chiquín, Eric Noé; Gutiérrez-Orrego, Axel; Morán-Ical, Sergio (2011-12-01). "Reorganization of a deeply incised drainage: role of deformation, sedimentation and groundwater flow". Basin Research. 23 (6): 631–651. Bibcode:2011BasR...23..631B. doi:10.1111/j.1365-2117.2011.00510.x. ISSN 1365-2117.
  6. Lyon-Caen, H.; Barrier, E.; Lasserre, C.; Franco, A.; Arzu, I.; Chiquin, L.; Chiquin, M.; Duquesnoy, T.; Flores, O. (2006-10-01). "Kinematics of the North American–Caribbean-Cocos plates in Central America from new GPS measurements across the Polochic-Motagua fault system" (PDF). Geophysical Research Letters. 33 (19): L19309. Bibcode:2006GeoRL..3319309L. doi:10.1029/2006GL027694. ISSN 1944-8007.
  7. White, Randall A. "The Guatemala earthquake of 1816 on the Chixoy-Polochic fault". Bulletin of the Seismological Society of America. 75 (2): 455–473.
  8. Brocard, Gilles; Anselmetti, Flavio S.; Teyssier, Christian (2016-11-15). "Guatemala paleoseismicity: from Late Classic Maya collapse to recent fault creep". Scientific Reports. 6 (1): 36976. Bibcode:2016NatSR...636976B. doi:10.1038/srep36976. ISSN 2045-2322. PMC 5109539. PMID 27845383.
  9. Guzmán-Speziale, Marco (2010-12-01). "Beyond the Motagua and Polochic faults: Active strike-slip faulting along the Western North America–Caribbean plate boundary zone". Tectonophysics. 496 (1–4): 17–27. Bibcode:2010Tectp.496...17G. doi:10.1016/j.tecto.2010.10.002.
  10. Franco, A.; Molina, E.; Lyon-Caen, H.; Vergne, J.; Monfret, T.; Nercessian, A.; Cortez, S.; Flores, O.; Monterosso, D. (2009-11-01). "Seismicity and Crustal Structure of the Polochic-Motagua Fault System Area (Guatemala)". Seismological Research Letters. 80 (6): 977–984. doi:10.1785/gssrl.80.6.977. ISSN 0895-0695.

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