Abstract
The Cocos plate subducts beneath North America at the Mexico trench. The northernmost segment of this trench, between the Orozco and Rivera fracture zones, has ruptured in a sequence of five large earthquakes from 1973 to 1985; the Jan. 30, 1973 Colima event (M s 7.5) at the northern end of the segment near Rivera fracture zone; the Mar. 14, 1979 Petatlan event (M s 7.6) at the southern end of the segment on the Orozco fracture zone; the Oct. 25, 1981 Playa Azul event (M s 7.3) in the middle of the Michoacan “gap”; the Sept. 19, 1985 Michoacan mainshock (M s 8.1); and the Sept. 21, 1985 Michoacan aftershock (M s 7.6) that reruptured part of the Petatlan zone. Body wave inversion for the rupture process of these earthquakes finds the best: earthquake depth; focal mechanism; overall source time function; and seismic moment, for each earthquake. In addition, we have determined spatial concentrations of seismic moment release for the Colima earthquake, and the Michoacan mainshock and aftershock. These spatial concentrations of slip are interpreted as asperities; and the resultant asperity distribution for Mexico is compared to other subduction zones. The body wave inversion technique also determines theMoment Tensor Rate Functions; but there is no evidence for statistically significant changes in the moment tensor during rupture for any of the five earthquakes. An appendix describes theMoment Tensor Rate Functions methodology in detail.
The systematic bias between global and regional determinations of epicentral locations in Mexico must be resolved to enable plotting of asperities with aftershocks and geographic features. We have spatially “shifted” all of our results to regional determinations of epicenters. The best point source depths for the five earthquakes are all above 30 km, consistent with the idea that the down-dip edge of the seismogenic plate interface in Mexico is shallow compared to other subduction zones. Consideration of uncertainties in the focal mechanisms allows us to state that all five earthquakes occurred on fault planes with the same strike (N65°W to N70°W) and dip (15±3°), except for the smaller Playa Azul event at the down-dip edge which has a steeper dip angle of 20 to 25°. However, the Petatlan earthquake does “prefer” a fault plane that is rotated to a more east-west orientation—one explanation may be that this earthquake is located near the crest of the subducting Orozco fracture zone. The slip vectors of all five earthquakes are similar and generally consistent with the NUVEL-predicted Cocos-North America convergence direction of N33°E for this segment. The most important deviation is the more northerly slip direction for the Petatlan earthquake. Also, the slip vectors from the Harvard CMT solutions for large and small events in this segment prefer an overall convergence direction of about N20°E to N25°E.
All five earthquakes share a common feature in the rupture process: each earthquake has a small initial precursory arrival followed by a large pulse of moment release with a distinct onset. The delay time varies from 4 s for the Playa Azul event to 8 s for the Colima event. While there is some evidence of spatial concentration of moment release for each event, our overall asperity distribution for the northern Mexico segment consists of one clear asperity, in the epicentral region of the 1973 Colima earthquake, and then a scattering of diffuse and overlapping regions of high moment release for the remainder of the segment. This character is directly displayed in the overlapping of rupture zones between the 1979 Petatlan event and the 1985 Michoacan aftershock. This character of the asperity distribution is in contrast to the widely spaced distinct asperities in the northern Japan-Kuriles Islands subduction zone, but is somewhat similar to the asperity distributions found in the central Peru and Santa Cruz Islands subduction zones. Subduction of the Orozco fracture zone may strongly affect the seismogenic character as the overlapping rupture zones are located on the crest of the subducted fracture zone. There is also a distinct change in the physiography of the upper plate that coincides with the subducting fracture zone, and the Guerrero seismic gap to the south of the Petatlan earthquake is in the “wake” of the Orozco fracture zone. At the northern end, the Rivera fracture zone in the subducting plate and the Colima graben in the upper plate coincide with the northernmost extent of the Colima rupture zone.
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References
Aki, K. (1979),Characterization of Barriers on an Earthquake Fault, J. Geophys. Res.84, 6140–6148.
Aki, K., andRichards, P. G.,Quantitative Seismology (Freeman, San Francisco 1980) 932 pp.
Astiz, L., Kanamori, H., andEissler, H. (1987),Source Characteristics of the Earthquakes in the Michoacan Seismic Gap in Mexico, Bull. Seismol. Soc. Am.77, 1326–1346.
Barker, J., andLangston, C. (1981),Inversion of Teleseismic Body Waves for the Moment Tensor of the 1978 Thessaloniki, Greece Earthquake, Bull. Seismol. Soc. Am.71, 1423–1444.
Beck, S. L., andChristensen, D. H. (1991),Rupture Process of the February 4, 1965, Rat Islands Earthquake, J. Geophys. Res.96, 2205–2221.
Beck, S., andRuff, L. (1985),The Rupture Process of the 1976 Mindanao Earthquake, J. Geophys. Res.90, 6773–6782.
Beck, S., andRuff, L. (1987),Rupture Process of the Great 1963 Kurile Islands Earthquake Sequence: Asperity Interaction and Multiple Event Rupture, J. Geophys. Res.92, 14123–14138.
Beck, S., andRuff, L. (1989),Great Earthquakes and Subduction along the Peru Trench, Phys. Earth Planet. Int.57, 199–224.
Byrne, D. E., Davies, D. M., andSykes, L. R. (1988),Loci and Maximum Size of Thrust Earthquakes and the Mechanics of the Shallow Region of Subduction Zones, Tectonics7, 833–857.
Chael, E. P., andStewart, G. S. (1982),Recent Large Earthquakes along the Middle America Trench and their Implications for the Subduction Process, J. Geophys. Res.87, 329–338.
Das, S., andAki, K. (1977),Pault Planes with Barriers: A Versatile Earthquake Model, J. Geophys. Res82, 5658–5670.
DeMets, C., Gordon, R. G., Argus, D. F., andStein, S. (1990),Current Plate Motions, Geophys. J. Int.101, 425–478.
Dewey, J. W., andSpence, W. (1979),Seismic Gaps and Source Zones of Recent Large Earthquakes in Coastal Peru, Pure and Appl. Geophys.117, 1148–1171.
Dmowska, R., andLi, V. C. (1982),A Mechanical Model of Precursory Source Processes for Some Large Earthquakes, Geophys. Res. Lett.9, 393–396.
Dziewonski, A. M., andWoodhouse, J. H. (1983),An Experiment in Systematic Study of Global Seismicity: Centroid Moment Tensor Solutions for 201 Moderate and Large Earthquakes of 1981. J. Geophys. Res.88, 3247–3271.
Eissler, H., Astiz, L., andKanamori, H. (1986),Tectonic Setting and Source Parameters of the September 19, 1985 Michoacan, Mexico Earthquake, Geophys. Res. Lett.13, 569–572.
Ekström, G. (1989),A Very Broad Band Inversion Method for the Recovery of Earthquake Source Parameters, Tectonophysics166, 73–100.
Ekström, G., andDziewonski, A. M. (1986),A Very Broad Band Analysis of the Michoacan, Mexico Earthquake of September 13, 1985, Geophys. Res. Lett.13, 605–608.
Gettrust, J. F., Hsu, V., Helsley, C. E., Herrero, E., andJordan, T. (1981),Pattern of Seismicity Preceding the Petatlan Earthquake of 14 March 1979, Bull. Seismol. Soc. Am.71, 761–770.
Gutenberg, B., andRichter, C. F. (1956),Magnitude and Energy of Earthquakes, Ann. Geofis. Rome9, 1–15.
Haskell, N. A. (1964),Total Energy and Energy Spectral Density of Elastic Wave Radiation from Propagating Faults, Bull. Seismol. Soc. Am.54, 1811–1842.
Haskov, J., Singh, S. K., Nava, E., Dominguez, T., andRodriguez, M. (1983),Playa Azul, Michoacan, Mexico Earthquake of 25 October 1981 (M s =7.3), Bull. Seismol. Soc. Am.73, 449–457.
Hotelling, H. (1936),Relation between Two Sets of Variates, Biometrika28, 321–377.
Houston, H., andKanamori, H. (1986),Source Characteristics of the 1985 Michoacan, Mexico Earthquake at Periods of 1 to 30 Seconds, Geophys. Res. Lett.13, 597–600.
Hsu, V., Helsley, C. E., Berg, E., andNovelo-Casanova, D. A. (1985),Correlation of Foreshocks and Aftershocks and Asperities, Pure and Appl. Geophys.122, 878–893.
Jarrard, R. D. (1986),Relation among Subduction Parameters, Rev. Geophysics24, 217–284.
Kanamori, H. (1977),The Energy Release in Great Earthquakes, J. Geophys. Res.82, 2981–2987.
Kanamori, H.,The nature of seismicity patterns before large earthquakes. InEarthquake Prediction—An International Review (D. Simpson and P. Richards, eds.), (AGU, Washington D.C. 1981), pp. 1–19.
Kanamori, H., Mori, J., Hauksson, E., Heaton, T., Hutton, L., andJones, L. (1993),Determination of Earthquake Energy Release and M L Using TERRAscope. Bull. Seismol. Soc. Am.83, 330–346.
Kikuchi, M.,Strength and stickiness of earthquake source. InProceedings of Internat. Sympos. Earthquake Source Physics and Earthquake Precursors (University of Tokyo, 1990) pp. 163–166.
Kikuchi, M., andFukao, Y. (1988),Seismic Wave Energy Inferred from Long-period Body Wave Inversion, Bull. Seismol. Soc. Am.78, 1707–1724.
Kostrov, B. V., andDas, S.,Principles of Earthquake Source Mechanics (Cambridge University Press, Cambridge 1988) 286 pp.
Lay, T., Kanamori, H., andRuff, L. (1982),The Asperity Model and the Nature of Large Subduction Zone Earthquakes, Earthquake Pred. Res.1, 3–71.
Madariaga, R. (1977),High-frequency Radiation from Crack (Stress Drop) Models of Earthquake Faulting, Geophys. J. Roy. Astron. Soc.51, 625–651.
McCann, W. R., andHabermann, R. E. (1989),Morphologic and Geologic Effects of the Subduction of Bathymetric Highs, Pure and Appl. Geophys.129, 41–69.
McNally, K. C., andMinster, J. B. (1981),Non-uniform Seismicity Rates along the Middle America Trench, J. Geophys. Res.86, 4949–4959.
Mendez, A. J., andAnderson, J. G. (1991),The Temporal and Spatial Evolution of the 19 September 1985 Michoacan Earthquake as Inferred from Near-source Ground Motion Records, Bull. Seismol. Soc. Am.81, 844–861.
Mendoza, C. (1993),Coseismic Slip of Two Large Mexican Earthquakes from Teleseismic Body Waveforms: Implications for Asperity Distribution in the Michoacan Plate-boundary Segment, J. Geophys. Res. submitted.
Mendoza, C., andHartzell, S. H. (1988),Aftershock Patterns and Mainshock Faulting, Bull. Seismol. Soc. Am.78, 1438–1449.
Mendoza, C., andHartzell, S. H. (1989),Slip Distribution of the 19 September 1985 Michoacan, Mexico Earthquake: Near-source and Teleseismic Constraints, Bull. Seismol. Soc. Am.79, 655–669.
Nabelek, J.,Determination of earthquake Source Parameters from Inversion of Body Waves, Ph.D. Thesis (Mass. Inst. of Technol. Cambridge, 1984) 346 pp.
Nishenko, S. P. (1991),Circum-Pacific Seismic Potential: 1989–1999, Pure and Appl. Geophys.135, 169–259.
Nur, A., andBen-Avraham, Z. (1983),Volcanic Gaps due to Oblique Consumption of Aseismic Ridges, Tectonophysics99, 355–362.
Ohnaka, M. (1992),Earthquake Source Nucleation: A Physical Model for Short-term Precursors, Tectonophysics211, 149–178.
Priestley, K. F., andMasters, T. G. (1986),Source Mechanism of the September 19, 1985 Michoacan Earthquake and its Implications, Geophys. Res. Lett.13, 601–604.
Reyes, A., Brune, J. N., andLomnitz, C. (1979),Source Mechanism and Aftershock Study of the Colima, Mexico Earthquake of January 20, 1973, Bull. Seismol. Soc. Am.69, 1819–1840.
Riedesel, M. A., Jordan, T. H., Sheehan, A. F., andSilver, P. G. (1986),Moment-tensor Specira of the 19 Sept. 85 and 21 Sept. 1985 Michoacan, Mexico Earthquakes, Geophys. Res. Lett.13, 609–612.
Rikitake, T. (1976),Recurrence of Great Earthquakes at Subduction Zones, Tectonophysics35, 335–362.
Ruff, L.,Fault asperities inferred from seismic body waves. InEarthquakes: Observation, Theory, and Interpretation (Kanamori, H. and Boschi, E., eds.) (North-Holland, Amsterdam 1983) pp. 251–276.
Ruff, L. (1984),Tomographic Imaging of the Earthquake Rupture Process, Geophys. Res. Lett.11, 629–632.
Ruff, L.,Tomographic imaging of seismic sources. InSeismic Tomography (Nolet, G., ed.) (Reidel, Dordrecht, Holland 1987) 386 pp.
Ruff, L. (1989a),Do trench sediments affect great earthquake occurrence in subduction zones? InSubduction Zones, Part II (Ruff, L. and Kanamori, H., eds.), Pure and Appl. Geophys.129, 263–282.
Ruff, L. J. (1989b),Multi-trace Deconvolution with Unknown Trace Scale Factors: Omnilinear Inversion of P and S Waves for Source Time Functions, Geophys. Res. Lett.16, 1043–1046.
Ruff, L. J. (1992a),Asperity Distributions and Large Earthquake Occurrence in Subduction Zones, Tectonophysics211, 61–83.
Ruff, L. J.,Seismic energy release of great subduction earthquakes: Can irregular rupture models explain the “missing” energy? Extended Abstract inWadati Conference on Great Subduction Earthquakes (Christensen, D., Wyss, M., Habermann, R., and Davies, J., eds.) (University of Alaska, Fairbanks 1992b) pp. 12–14.
Ruff, L., andKanamori, H. (1983a),Seismic Coupling and Uncoupling at Subduction Zones, Tectonophysics99, 99–117.
Ruff, L., andKanamori, H. (1983b),The Rupture Process and Asperity Distribution of Three Great Earthquakes from Long-period Diffracted P Waves, Phys. Earth Planet. Int.31, 202–230.
Ruff, L., andTichelaar, B. (1990),Moment Tensor Rate Functions for the 1989 Loma Prieta Earthquake, Geophys. Res. Lett.17, 1187–1190.
Schell, M., andRuff, L. (1989),Rupture of a Seismic Gap in Southeastern Alaska: The 1972 Sitka Earthquake (M s 7.6), Phys. Earth Planet. Int.54, 241–257.
Scholz, C. H.,The Mechanics of Earthquakes and Faulting (Cambridge University Press, New York 1990) 439 pp.
Schwartz, S., andRuff, L. (1987),Asperity Distribution and Earthquake Occurrence in the Southern Kurile Islands Ard, Phys. Earth Planet. Int.49, 54–77.
Singh, S. K., andLermo, J. (1985),Mislocation of Mexico Earthquakes as Reported in International Bulletins, Geof. Int.24 (2), 333–351.
Singh, S. K., andMortera, F. (1991),Source Time Functions of Large Mexican Subduction Earthquakes, Morphology of the Benioff Zone, Age of the Plate, and their Tectonic Implications, J. Geophys. Res.96, 21,487–21,502.
Singh, S. K., andOrdaz, M. (1993),Seismic Energy Release in Mexican Subduction Zone Earthquakes, preprint.
Singh, S. K., Rodriguez, M., andEspindola, J. M. (1984),A Catalog of Shallow Earthquakes of Mexico from 1900–1981, Bull. Seismol. Soc. Am.74, 267–279.
Sipkin, S. (1986a),Estimation of Earthquake Source Parameters by the Inversion of Waveform Data: Global Seismicity 1981–1983, Bull. Seismol. Soc. Am.76, 1515–1541.
Sipkin, S. (1986b),Interpretation of Non-double-couple Earthquake Mechanisms Derived from Moment Tensor Inversion, J. Geophys. Res.91, 531–549.
Stolte, C., McNally, K. C., Gonzalez-Ruiz, J., Simila, G. W., Reyes, A., Rebollar, C., Munguia, L., andMendoza, L. (1986),Fine Structure of a Postfailure Wadati-Benioff Zone, Geophys. Res. Lett.13, 577–580.
Stump, B. W., andJohnson, L. R. (1977),The Determination of Source Properties by the Linear Inversion of Seismograms, Bull. Seismol. Soc. Am.67, 1489–1502.
Tajima, F., Ruff, L., Kanamori, H., Zhang, Z., andMogi, K. (1990),Earthquake Source Processes and Subduction Regime in the Santa Cruz Islands Region, Phys. Earth Planet. Int.61, 269–290.
Tichelaar, B. W., Christensen, D. H., andRuff, L. J. (1992),Depth Extent of Rupture of the 1981 Chilean Outer-rise Earthquake as Inferred from Long-period Body Waves, Bull. Seismol. Soc. Am.82, 1236–1252.
Tichelaar, B. W., andRuff, L. J. (1991),Seismic Coupling along the Chilean Subduction Zone, J. Geophys. Res.96, 11,997–12,022.
Tichelaar, B. W., andRuff, L. J. (1993),Depth of Seismic Coupling along Subduction Zones, J. Geophys. Res.98, 2017–2037.
UNAM Seismology Group (1986),The September 1985 Michoacan Earthquakes: Aftershock Distribution and History of Rupture, Geophys. Res. Lett.13, 573–576.
Uyeda, S., andKanamori, H. (1979),Back-arc Opening and the Mode of Subduction, J. Geophys. Res.84, 1049–1061.
Valdes, C., Meyer, R. P., Zuniga, R., Haskov, J., andSingh, S. K. (1982),Analysis of the Petatlan Aftershocks: Numbers, Energy Release, and Asperities, J. Geophys. Res.87, 8519–8527.
Vasco, D. W. (1989),Deriving Source-time Functions Using Principal Component Analysis, Bull. Seismol. Soc. Am.79, 711–730.
Yomogida, K. (1988),Crack-like Rupture Processes Observed in Near-fault Strong Motion Data, Geophys. Res. Lett.15, 1223–1226.
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Ruff, L.J., Miller, A.D. Rupture process of large earthquakes in the northern Mexico subduction zone. PAGEOPH 142, 101–172 (1994). https://doi.org/10.1007/BF00875970
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DOI: https://doi.org/10.1007/BF00875970