Ž . Physics of the Earth and Planetary Interiors 115 1999 247–257 www.elsevier.comrlocaterpepi S wave attenuation in the coastal region of Jalisco–Colima, Mexico ´ F. Alejandro Nava a, ) , Rosalıa Garcıa-Arthur a , Raul R. Castro a , Carlos Suarez b , ´ ´ ´ Bertha Marquez b , Francisco Nunez-Cornu c , Gustavo Saavedra c , Roberto Toscano d ´ ´˜ ´ a ( ) Centro de InÕestigacion Cientıfica y Educacion Superior de Ensenada CICESE , Apdo. Postal 2732, Ensenada, B.C., 22800, Mexico ´ ´ ´ b ( ) Facultad de Geografıa, UniÕersidad de Guadalajara UG , Guadalajara, Jalisco, Mexico ´ c Centro UniÕersitario de la Costa, UG, Puerto Vallarta, Jalisco, Mexico d Facultad de Fısica, UG, Guadalajara, Jalisco, Mexico ´ Received 8 September 1998; accepted 5 June 1999 Abstract Aftershock data from the October 9, 1995, M s7.6 earthquake, that occurred in the coastal subduction region of Colima–Jalisco, Mexico, are used to obtain estimates of the frequency independent quality factor Q and spectral decay s parameter k , in the approximate frequency range 3 Hz Ff F40 Hz, as functions of hypocentral distance r. A regression analysis results in the relations for S waves: Q s261.397 q3.198 r "15.536 s k s0.009651 q0.000462 r "0.0012. The observed distance dependence of Q and k is similar to that reported for the Mexican regions of Oaxaca and Guerrero. s Our Q values agree with those reported for Oaxaca and northern Baja CA for frequencies around 8 Hz, and are somewhat s Ž . lower a factor of ;0.8 to ;0.5 for higher frequencies around 20 Hz; however, they are significantly lower than all but the lowest values reported for the Guerrero region, attaining factors ;0.25 and ;0.13 for frequency ranges around 8 and 20 Hz, respectively. It thus appears that the Guerrero region has an anomalously low attenuation compared with the flanking coastal regions of Oaxaca–Chiapas to the SE and Jalisco–Colima to the NW. q 1999 Elsevier Science B.V. All rights reserved. Keywords: S wave attenuation; Jalisco–Colima; Earthquake ) Corresponding author. Tel.: q52-61-744501; fax: q52-61-750559; e-mail: fnava@cicese.mx 0031-9201r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0031-9201 99 00114-4