DEFORMATIONS IN THE MIDDLE AMERICA TRENCH ACCORDING TO EARTHQUAKE FOCAL MECHANISMS AND THEIR FEATURES IN THE AREA OF THE 2017 МW 8.2 CHIAPAS EARTHQUAKE, MEXICO

Seismotectonic deformations in the Middle America Trench and their features in the area of preparation of the Chiapas earthquake, М_W=8.2, 08 September 2017, were determined using the data on 2244 focal mechanisms of earthquakes for the period of 1977–2017. The distribution of seismicity with depth was studied in detail. The decrease in the depth of the Benioff zone in the north-western subduction segments and the increase in the south-eastern segments is associated with the age of the subducting parts of the Cocos plate and the angle of their immersion. The latter mechanism can also explain the presence of earthquakes with normal focal mechanism on the oceanic uplift in the south-eastern segments of the subduction zone and their absence in the north-western ones. In general, the typical character of subduction deformations has a number of features in the Middle America Trench. The predominance of shortening by horizontal components and elongation by vertical ones at depths up to 35 km is replaced by the transitional type with mosaic distribution of deformations of different signs in the depth range of 36–70 km. Even lower, in the depth range of 70–105 km, the type of deformation changes to the opposite with respect to the upper horizon. The Chiapas earthquake occurred on the border of regions with different types of deformation, which indicates softening of the block’s medium to the west of the hypocenter and its hardening to the east. Such a state of the lithospheric medium may indicate the presence of a deformation shadow zone in the Chiapas earthquake preparation area.

1. Alvarado G.E., Benito B., Staller A., Climent Á., Camacho E., Rojas W., Marroquín G., Molina E., Talavera J.E., MartínezCuevas S., Lindholm C., 2017. The New Central American Seismic Hazard Zonation: Mutual Consensus Based on up to Day Seismotectonic Framework. Tectonophysics 721, 462–476. https://doi.org/10.1016/j.tecto.2017.10.013.

2. Ambraseys’ N.N., Adams R.D., 1996. Large-Magnitude Central American Earthquakes, 1898–1994 Geophysical Journal International 127, 665–692. https://doi.org/10.1111/j.1365-246X.1996.tb04046.x.

3. Anderson J.G., Singh S.K., Espindola J.M., Yamamoto J., 1989. Seismic Strain Release in the Mexican Subduction Thrust. Physics of the Earth and Planetary Interiors 58 (4), 307–322. https://doi.org/10.1016/0031-9201(89)90102-7.

4. Benz H.M., Dart R.L., Villaseñor A., Hayes G.P., Tarr A.C., Furlong K.P., Rhea S., 2011. Seismicity of the Earth 1900– 2010. Mexico and Vicinity. Available from: https://pubs.usgs.gov/of/2010/1083/f/.

5. Bulletin of the International Seismological Centre catalog search, 2019. Available from: http://www.isc.ac.uk/iscbulletin/search.

6. Bushenkova N.A., Kuchai O.A., Chervov V.V., 2018. Submeridional Boundary Zone in Asia: Seismicity, Lithosphere Structure and the Distribution of Convective Flows in the Upper Mantle. Geodynamics & Tectonophysics 9 (3), 1007– 1023 (in Russian) [Бушенкова Н.А., Кучай О.А., Червов В.В. Субмеридиональная пограничная зона в Азии: сейсмичность, структура литосферы и распределение конвективных потоков в верхней мантии // Геодинамика и тектонофизика. 2018. Т. 9. № 3. C. 1007–1023]. https://doi.org/10.5800/GT-2018-9-3-0381.

7. Cáceres D., 2003. Earthquake Sources and Hazard in Northern Central America. Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 834. Uppsala, 29 p.

8. Dyad’kov P.G., Kuchai O.A., Romanenko Yu.M., 2017. Seismotectonic Deformations of the Contact Zone of the Nazca and South American Lithospheric Plates Relation to the February 27, 2010 Mw 8.8 Maule Еarthquake. Geodynamics & Tectonophysics 8 (3), 655–671 (in Russian) [Дядьков П.Г., Кучай О.А., Романенко Ю.М. Сейсмотектонические деформации зоны контакта литосферных плит Наска и Южно-Американской в связи с землетрясением Мауле, М w 8.8, 27.02.2010 // Геодинамика и тектонофизика. 2017. Т. 8. № 3. C. 655–671]. https://doi.org/10.5800/GT-2017-8-3-0311.

9. Dyad’kov P.G., Mikheeva A.V., 2010. The Expert Earthquake Database (EEDB) for Seismic-Geodynamic Research. Bulletin of the Novosibirsk Computing Center. Series: Mathematical Modeling in Geophysics 13, 15–30.

10. Ellis A., Demets C., Briole P., Cosenza B., Flores O., 2018. GPS Constraints on Deformation in Northern Central America from 1999 to 2017, Part 1 – Time-Dependent Modelling of Large Regional Earthquakes and Their Post-Seismic Effects. Geophysical Journal International 214 (3), 2177– 2194. https://doi.org/10.1093/gji/ggy249.

11. Franco A., Lasserre C., Lyon-Caen H., Kostoglodov V., Molina E., Guzman-Speziale M., Monterosso D., Robles V., Figueroa C., Amaya, Barrier E., Chiquin L., Moran S., Flores O., Romero J., Santiago J. A., Manea M., Manea V. C., 2012. Fault Kinematics in Northern Central America and Сoupling Along The subduction Interface of the Cocos Plate, from GPS Data in Chiapas (Mexico), Guatemala and El Salvador. Geophysical Journal International 189, 1223–1236. https://doi.org/10.1111/j.1365-246X.2012.05390.x.

12. Gol’din S.V., Kuchai O.A., 2007. Seismic Strain in the AltaiSayan Active Seismic Area and Elements of Collisional Geodynamics. Russian Geology and Geophysics 48, 536–557. https://doi.org/10.1016/j.rgg.2007.06.005.

13. Khain V.E., Lomize M.G., 1995. Geotectonics and Fundamentals of Geodynamics. Moscow State University, Moscow, 480 p. (in Russian) [Хаин В.Е., Ломизе М.Г. Геотектоника с основами геодинамики. M.: МГУ, 1995. 480 с.].

14. Kim Y., Clayton R.W., Jackson J.M, 2010 Geometry and Seismic Properties of the Subducting Cocos Plate in Central Mexico. Journal of Geophysical Research: Solid Earth 115, B06310. https://doi.org/10.1029/2009JB006942.

15. Kostrov B.V., 1975. Mechanics of Earthquake Source. Nauka, Moscow, 176 p. (in Russian) [Костров Б.В. Механика очага тектонического землетрясения. М.: Наука, 1975. 176 с.].

16. Kuchai O.A., Bushenkova N.A., Tataurova A.A., 2015. Structure of the Lithosphere and Seismotectonic Deformations in Contact Zone of Lithospheric Plates in the Sumatra Island region. Geodynamics & Tectonophysics 6 (1), 77–89 (in Russian) [Кучай О.А., Бушенкова Н.А., Татаурова А.А. Структура литосферы и сейсмотектонические деформации зоны контакта литосферных плит в районе острова Суматра // Геодинамика и тектонофизика. 2015. Т. 6. № 1. С. 77–89. https://doi.org/10.5800/GT-2015-6-1-0173.

17. Kuchai O.A., Dyadkov P.G., Romanenko Yu.M., Dzhumagalieva Z.S., 2018. Seismotectonic Deformations in the Mexican Subduction Zone. In: Subsoil Use. Mining. Directions and Technologies for Search, Exploration and Development of Mineral Deposits. Economics. Geoecology: Proceedings of International Scientific Conference. Vol. 3. Novosibirsk, p. 207–214 (in Russian) [Кучай О.А., Дядьков П.Г., Романенко Ю.М., Джумагалиева З.С. Сейсмотектонические деформации в Мексиканской cубдукционной зоне // Недропользование. Горное дело. Направления и технологии поиска, разведки и разработки месторождений полезных ископаемых. Экономика. Геоэкология: Материалы Международной научной конференции. 2018. Т. 3. С. 207–214].

18. Kuchai O.A., Kozina M.E., 2015. Regional Features of Seismotectonic Deformations in East Asia Based on Earthquake Focal Mechanisms and Their Use for Geodynamic Zoning. Russian Geology and Geophysics 10, 1491–1499. https://doi.org/10.1016/j.rgg.2015.09.011.

19. Kyriakopoulos C., Newman A.V., Thomas A.M., MooreDriskell M., Farmer G.T., 2015. A New Seismically Constrained Subduction Interface Model for Central America. Journal of Geophysical Research: Solid Earth 120 (8), 1–13. https://doi.org/10.1002/2014JB011859.

20. Lefeldt M., Grevemeyer I., 2008. Centroid Depth and Mechanism of Trench-Outer Rise Earthquakes. Geophysical Journal International 172 (1), 240–251. https://doi.org/10.1111/j.1365-246X.2007.03616.x.

21. Manea V.C., Manea M., 2011. Flat-Slab Thermal Structure and Evolution beneath Central Mexico. Pure Applied Geophysics 168, 1475–1487. https://doi.org/10.1007/s00024-010-0207-9.

22. Mikheeva A.V., Marchuk An.G., Dyadkov P.G., 2014. Geoinformation Systems for Studying Seismicity and Impact Cratering Using Remote Sensing Data. In: Dayana Nelson (Ed.), Geographic Information Systems (GIS): Techniques, Applications and Technologies. Nova Science Publishers, p. 151–215.

23. Pardo M., Sufirez G., 1995. Shape of the Subducted Rivera and Cocos Plates in Southern Mexico: Seismic and Tectonic Implications. Journal of Geophysical Research: Solid Earth 100 (B7), 12357–12377. https://doi.org/10.1029/95JB00919.

24. Pérez-Campos X., Kim Young Hee, Husker A., Davis P.M., Clayton R.W., Iglesias A., Pacheco J.F., Singh S.K., Manea V.C., Gurnis M., 2008. Horizontal Subduction and Truncation of the Cocos Plate beneath Central Mexico. Geophysical Research Letters 35, L18303. https://doi.org/10.1029/2008GL035127.

25. Ramírez-Gaytán A., Bandy W. L., Jaimes M. A., SalidoRuiz R. A., Preciado A., Huérfano V. and Cárdenas-Monroy C., 2015. Analysis of the Unusual Earthquake of 13 August 2006 in Michoacán, México. Journal of Volcanology and Seismology 9 (6), 412–428. https://doi.org/10.1134/S0742046315060068.

26. Ranero C.R., Villasenör A., Morgan J.P., Weinrebe W., 2005. Relationship between Bend-Faulting at Trenches and Intermediate-Depth Seismicity. Geochemistry, Geophysics, Geosystem 6 (12), 1525–2027. https://doi.org/10.1029/2005GC000997.

27. Rebetsky Yu.L., 2007. Tectonic Stresses and Strength of Natural Mountain Ranges. Akademkniga, Moscow, 406 p. (in Russian) [Ребецкий Ю.Л. Тектонические напряжения и прочность природных горных массивов. М.: ИКЦ Академкнига, 2007. 406 с.].

28. Rebetsky Yu.L., Kuchai O.A., Marinin A.V. 2013. Stress and Deformation of the Earth’s Crust in the Altai-Sayan Mountainous Area. Russian Geology and Geophysics 54 (2), 206– 222. https://doi.org/10.1016/j.rgg.2013.01.011.

29. Rebetsky Yu.L., Kuchai O.A., Sycheva N.A., Tatevossian R.E., 2012. Development of Inversion Methods on Fault Slip Data Stress State in Orogenes of the Central Asia. Tectonophysics 581, 114–131. https://doi.org/10.1016/j.tecto.2012.09.027.

30. Rebetsky Yu.L, Marinin A.V., 2006. Preseismic Stress Field before the Sumatra-Andaman Earthquake of 26.12.2004: A Model of Metastable State of Rocks. Russian Geology and Geophysics 47 (11), 1173–1185.

31. Rebetsky Yu.L., Polets A.Yu., 2014. The State of Stresses of the Lithosphere of Japan before the Catastrophic Tohoku Earthquake of 11 March 2011. Geodynamics & Tectonophysics 5 (2), 469–506 (in Russian) [Ребецкий Ю.Л., Полец А.Ю. Напряженное состояние литосферы Японии перед катастрофическим землетрясением Тохоку 11.03.2011 // Геодинамика и тектонофизика. 2014. Т. 5. № 2. С. 469– 506]. https://doi.org/10.5800/GT-2014-5-2-0137.

32. Riznichenko Yu.V., 1985. Problems of Seismology. Nauka, Moscow, 408 p. (in Russian) [Ризниченко Ю.В. Проблемы сейсмологии. М.: Наука, 1985. 408 с.].

33. Santoyo M.A., Mikumo T., Quintanar L., 2006. Faulting Process and Coseismic Stress Change during the 30 January, 1973, Colima, Mexico Interplate Earthquake (Mw=7.6). Geofísica Internacional 45 (3), 163–178.

34. Stubailo I., Beghein C., Davis P.M., 2012. Structure and Anisotropy of the Mexico Subduction Zone Based on RayleighWave Analysis and Implications for the Geometry of the TransMexican Volcanic Belt. Journal of Geophysical Research 117, B05303. https://doi.org/10.1029/2011JB008631.

35. USGS Earthquake Hazards Program, NEIC catalog search, 2017. Available from: https://www.usgs.gov/naturalhazards/earthquake-hazards/earthquakes.

36. Wang S.-C., McNally K.C., Geller R.J., 1982. Seismic Strain Release along the Middle America Trench. Mexico Geophysical Research Letters 9 (3), 182–185. https://doi.org/10.1029/GL009i003p00182.

37. Ye L., Lay T., Bai Y., Cheung K.F., Kanamori H., 2017. The 2017 M w 8.2 Chiapas, Mexico, Earthquake: Energetic Slab Detachment. Geophysical Research Letters 44, 11824–11832. https://doi.org/10.1002/2017GL076085.

38. Ye L., Lay T., Kanamori H., 2013. Large Earthquake Rupture Process Variations on the Middle America Megathrust. Earth and Planetary Science Letters 381, 147–155. https://doi.org/10.1016/j.epsl.2013.08.042.

39. Yunga S.L., 1990. Methods and Results of Seismotectonic Deformation Studies. Nauka, Moscow, 191 p. (in Russian) [Юнга С.Л. Методы и результаты изучения сейсмотектонических деформаций. М.: Наука, 1990. 191 с.].