IMPLICATIONS OF THE OCTOBER 1995 COLIMA-JALISCO MEXICO EARTHQUAKES ONTHE RIVERA NORTH-AMERICA EULER VECTOR

Rivera-North America Euler vectors fail into three groups based on the predicted motion of the Rivera plate relative to the North America pl ate along the Middle America Trench north of 18.5 degrees N. Namely, t hose that predict (1) a slow, more easterly directed motion, (2) a slo w, more northerly directed motion, and (3) a faster, more northerly di rected motion. The focal mechanism solution, rupture area and seismic moment of the great (M(W)=8.0) Colima-Jalisco, Mexico, earthquake of O ctober 9, 1995 and its foreshocks and aftershocks provide additional c onstraints on the Rivera-North America Euler vector. The slip directio n (N30 degrees E) of the main event clearly favors those Euler poles w hich predict a more northerly direction of motion. This direction lies within 5 degrees of those predicted by these poles, whereas, it diffe rs by between 9 degrees and 18 degrees from those poles which predict a more easterly motion. The amount of slip which occurred during the m ain event suggests a minimum convergence rate of between 4.3 and 6.5 c m/yr. This favors Euler vectors which predict higher convergence rates , however, a firm conclusion cannot be made due to the uncertainty in the recurrence time estimation. A new Rivera-North America Euler pole, calculated incorporating the information provided by the 1995 events, lies at 21.87 degrees N, 109.58 degrees W. It predicts a N30.3 degree s E directed motion of the Rivera plate relative to North America at t he location of the main event; a difference of only 0.3 degrees from t he slip direction of the main event.