Advertisement

The 2006 Bahía Asunción Earthquake Swarm: Seismic Evidence of Active Deformation Along the Western Margin of Baja California Sur, Mexico

  • Luis Munguía
  • Sergio Mayer
  • Alfredo Aguirre
  • Ignacio Méndez
  • Mario González-Escobar
  • Manuel Luna
Chapter
Part of the Pageoph Topical Volumes book series (PTV)

Abstract

The study of the Bahía Asunción earthquake swarm is important for two reasons. First, the earthquakes are clear evidence of present activity along the zone of deformation on the Pacific margin of Baja California. The swarm, with earthquakes of magnitude Mw of up to 5.0, occurred on the coastline of the peninsula, showing that the Tosco-Abreojos zone of deformation is wider than previously thought. Second, the larger earthquakes in the swarm caused some damage and much concern in Bahía Asunción, a small town located in the zone of epicenters. We relocated the larger earthquakes with regional and/or local seismic data. Our results put the earthquake sources below the urban area of Bahía Asunción, at 40–50 km to the north of the teleseismically determined epicenters. In addition, these new locations are in the area of epicenters of many smaller events that were located with data from local temporary stations. This area trends in an E–W direction and has dimensions of approximately 15 km by 10 km. Most earthquakes had sources at depths that are between 4 and 9 km. A composite focal mechanism for the smaller earthquakes indicated right-lateral strike–slip motion and pure-normal faulting occurred during this swarm. Interestingly, the ANSS earthquake catalog of the United States Geological Survey (USGS) reported each one of these faulting styles for two large events of the swarm, with one of these earthquakes occurring 2 days before the other one. We associate the earthquake with strike–slip mechanism with the San Roque Fault, and the earthquake with the normal faulting style with the Asunción Fault. However, there is need of further study to verify this possible relation between the faults and the earthquakes. In addition, we recorded peak accelerations of up to 0.63g with an accelerometer installed in Bahía Asunción. At this site, an earthquake of Mw 4.9 produced those high values at a distance of 4.1 km. We also used the acceleration dataset from this site to estimate the linear response of sediments lying beneath the station. The resulting average amplification function has a fundamental resonance frequency of about 5 Hz and shows amplification factors of 2–4 for motions at frequencies in the range 2–8 Hz. A comparison of this amplification function with the response of soils to shaking from larger events shows that above 20 Hz the amplification of motion in the larger events decreases relative to the weak-motion response.

Keywords

Pacific margin of Baja California Sur earthquake swarm in Bahía Asunción transtensional deformation high ground accelerations from moderate magnitude earthquakes 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Borcherdt, R. D. (1994). Estimates of Site-Dependent Response Spectra for Design (Methodology and Justification). Earthquake Spectra, vol. 10(4), pp. 617–653.Google Scholar
  2. Brothers, D., A. Harding, A. González-Fernández, W. S. Holbrook, G. Kent, N. Driscoll, J. Fletcher, D. Lizarralde, P. Umhoefer and G. Axen (2012). Farallon slab detachment and deformation of the Magdalena Shelf, southern Baja California, Geophys. Res. Lett., 39, L09307, doi: 10.1029/2011GL050828.CrossRefGoogle Scholar
  3. Castro, R. R., C. Valdés-González, P. Shearer, V. Wong, L. Astiz, F. Vernon, A. Pérez-Vertti, and A. Mendoza (2011). The 3 August 2009 Mw 6.9 Canal de Ballenas Region, Gulf of California, Earthquake and Its Aftershocks. Bull. Seism. Soc. Am., 101, No. 3, pp. 929–939, doi: 10.1785/0120100154.CrossRefGoogle Scholar
  4. Clayton, R.W., J. Trampert, C. Rebollar, J. Ritsema, P. Persaud, H. Paulssen, X. Pérez-Campos, A. Wettum, A. Pérez-Vertti, F. DiLuccio (2004). The NARS-Baja Seismic Array in the Gulf of California Rift Zone. Margins Newsletter, No. 13, 1–4.Google Scholar
  5. DeMets, C. A. (1995). Reappraisal of seafloor spreading lineations in the Gulf of California: implications for the transfer of Baja California to the Pacific plate and estimates of Pacific-North America motion, Geophys. Res. Lett., 22, 3545–3548.CrossRefGoogle Scholar
  6. DeMets, C. A. and Dixon, T. H. (1999). New kinematic models for Pacific-North America motion from 3 Ma to present, I: Evidence for steady motion and biases in the NUVEL-1A model, Geophysical Research Letters, 26, 1921–1924.CrossRefGoogle Scholar
  7. Fletcher, J. M., and L. Munguía (2000). Active continental rifting in southern Baja California, Mexico: implications for plate motion partitioning and the transition to sea floor spreading in the Gulf of California, Tectonics, 19, No. 6, 1107–1123.Google Scholar
  8. Fletcher, J.M., M. Grove, D. Kimbrough, O. Lovera, and G. E. Gehrels (2007). Ridge-trench interactions and the Neogene tectonic evolution of the Magdalena Shelf and southern Gulf of California: Insights from detrital zircon U-Pb ages from the Magdalena fan and adjacent areas. Geol. Soc. Am. Bull., 119; no. 11/12; pp. 1313–1336; doi: 10.1130/B26067.1.CrossRefGoogle Scholar
  9. Goff, J. A., E. A. Bergman, and S. C. Solomon (1987). Earthquake source mechanisms and transform fault tectonics in the Gulf of California, J. Geophys. Res., 92, 10,485–10,510.CrossRefGoogle Scholar
  10. Havskov, J., and L. Ottemöller (Editors) (2001). SEISAN: the earthquake analysis software for Windows, SOLARIS, and LINUX, Version 7.2. Manual, Institute of Solid Earth Physics, University of Bergen, Norway.Google Scholar
  11. Lermo, J., and F. J. Chavez-Garcia (1993). Site effects evaluation using spectral ratios with only one station, Bull. Seism. Soc. Am. 83, no. 5, 1574–1594.Google Scholar
  12. Lienert, B. R. E. and J. Havskov (1995). A computer program for locating earthquakes both locally and globally. Seismol. Res. Lett., 66:26–36.CrossRefGoogle Scholar
  13. Michaud, F., Sosson, M., Royer, J.-Y., Chabert, A., Bourgois, J., Calmus, T., Mortera, C., Bigot-Cormier, F., Bandy, W., Dyment, J., Pontoise, B., and Sichler, B. (2004), Motion partitioning between the Pacific plate, Baja California and the North America plate: The Tosco-Abreojos fault revisited: Geophysical Research Letters, v. 31, p. L08604, doi: 10.1029/2004GL019665.
  14. Michaud F, T. Calmus, M. Sosson, J-Y. Royer, J. Bourgois, A. Chabert, F. Bigot-Cormier, B. Bandy, C. Mortera-Gutiérrez (2005). La zona de falla Tosco-Abreojos: un sistema lateral derecho activo entre la placa Pacífico y la península de Baja California. Boletín de la Sociedad Geológica Mexicana. Tomo LVII, Núm. 1., pp. 53–63.Google Scholar
  15. Michaud, F., Calmus, T., Royer, J.-Y., Sosson, M., Bandy, B., Mortera-Gutiérrez, C., Dyment, J., Bigot-Cormier, F., Chabert, A., and Bourgois, J. (2007), Right lateral active faulting between southern Baja California and the Pacific plate: The Tosco-Abreojos fault, In Alanis-Alvarez, S. A. and Nieto-Samaniego, A. F., eds., Celebrating the Centenary of the Geological Society of Mexico: Geological Society of America, special paper 422, pp. 287–300, doi: 10.1130/2007.2422(09).
  16. Michaud, F., Calmus, T., Ratzov, G., Royer, J.-Y., Sosson, M., Bigot-Cormier, F., Bandy, W. and Mortera-Gutiérrez, C. (2011). Active deformation along the southern end of the Tosco-Abreojos fault system: New insights from multibeam swath bathymetry. Pure Appl. Geophys., 168(8–9), 1363–1372, doi: 10.1007/s00024-010-0193-y.CrossRefGoogle Scholar
  17. Munguía, L., M. Reichle, A. Reyes, R. Simons, and J. N. Brune (1977). Aftershocks of the 8 July, 1975 Canal de las Ballenas, Gulf of California, earthquake, Geophys. Res. Lett., 4, 507–509.CrossRefGoogle Scholar
  18. Munguía, L., M. González, S. Mayer, and A. Aguirre (2006). Seismicity and State of Stress in the La Paz–Los Cabos Region, Baja California Sur, Mexico. Bull. Seismol. Soc. Am., 96, No. 2, pp. 624–636, April 2006, doi: 10.1785/0120050114.CrossRefGoogle Scholar
  19. Munguía, L., M. González, M. Navarro, T. Valdez, S. Mayer, A. Aguirre, V. Wong, and M. Luna (Submitted to PAGEOPH, 2015). A local seismic study at the central part of the Magdalena Shelf, in the Pacific margin of Baja California Sur, Mexico.Google Scholar
  20. Nakamura, Y. (1989). A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface, Quarterly Report of the Railway Technical Research Institute 30, no. 1, pp. 25–33.Google Scholar
  21. Normark, W.R., J.E. Spencer, and J. Ingle (1987). Geology and Neogene history of the Pacific c continental margin of Baja California Sur, Mexico, in Scholl, D.W., et al., eds., Geology and resource potential of the continental margin of western North America and adjacent ocean basins—Beaufort Sea to Baja California: Houston, Texas, Circum-Pacific Counsel for Energy and Mineral Resources, Earth Science Series, 6, p. 449–472.Google Scholar
  22. Ortlieb, L. (1991). Quaternary Vertical Movements along the Coasts of Baja California and Sonora. In: J. P. Dauphin and B. T. Simoneit (Eds.), The Gulf and Peninsular province of the Californias, Amer. Asoc. Petrol. Geol. Mem., 47, pp. 447–480.Google Scholar
  23. Reichle, M. S., G. F. Sharman, and J. N. Brune (1976). Sonobuoy and teleseismic study of Gulf of California transform fault earthquake sequences. Bull. Seismol. Soc. Am., 66, No.5, pp. 1623 1641.Google Scholar
  24. Salazar, C. R. M. (2014). Evidencias estructurales y sismo estratigráficas en la parte central de la plataforma Magdalena, margen occidental de Baja California a partir de sísmica de reflexión. MsC. thesis, 89 pp., Centro de Investigación Científica y de Educación Superior de Ensenada, B. C., Ensenada, B. C., México.Google Scholar
  25. Seed, R. B., Chang, S. W., Dickenson, S. E., and Bray, J. D. (1997) “Site-Dependent Seismic Response Including Recent Strong Motion Data.” Proc., Special Session on Earthquake Geotechnical Engineering, XIV International Conf. On Soil Mechanics and Foundation Engineering, Hamburg, Germany, A. A. Balkema Publ., Sept. 6–12, pp. 125–134.Google Scholar
  26. Spencer, J. E. and Normark, W. R. (1979). Tosco-Abreojos fault zone: A Neogene transform plate boundary within the Pacific margin of southern Baja California, Mexico. Geology, V. 7, pp. 554–557.CrossRefGoogle Scholar

Copyright information

© Springer Basel 2015

Authors and Affiliations

  1. 1.División de Ciencias de la TierraCentro de Investigación Científica y de Educación Superior de Ensenada, B. C.EnsenadaMexico
  2. 2.Centro de Investigación Científica y de Educación Superior de Ensenada, B. C.La PazMexico

Personalised recommendations