3:30 PM - 4:30 PM
[J06-P-17] The long duration, April 18, 2002 (Mw 6.7), Mexico earthquake; a small tsunami earthquake next to the Guerrero Gap
We estimate the duration, extent and rupture velocity of the April 18, 2002 (Mw 6.7) earthquake. The hypocenter location (Pacheco & Singh, 2010) is inside what is known as the Guerrero Gap, a segment of the Mexican subduction zone that has not had a large earthquake in at least 100 years.
The 2002 earthquake is anomalous in the sense that it produced very small accelerations for its size (Iglesias et al 2003) and it is one of the earthquakes with longest duration relative to its magnitude recorded globally in the last 40 years (Duputel et al, 2013). Events of this type are particularly hazardous because they produce relatively large tsunamis (Kanamori, 1972) and small ground motions for their size, so they may be mistaken for smaller events by people near the coast, who may not prepare for the large tsunami. As near trench earthquakes are relatively rare, and due to their destruction potential, it is important to study in detail the few recorded events of this type.
The extent of the rupture area of the 2002 earthquake, is key to understanding the seismogenic potential of the Guerrero Gap. Often the rupture area of an earthquake is estimated by the extent of the aftershock area. However, locating earthquakes near the trench is difficult, due to their emerging P-waves and as they occur outside of the network of observation. In this study we calculate the duration of the 2002 earthquake by observations of far-field records. We use the difference in time between the first and last coherent signals in the peculiar P wavetrain of event, observed to conclude that the rupture had a duration and along strike length of approximately 56s and 60 km, respectively. The rupture propagated to the north-west with a rupture velocity of 1 km/s. To put further constraints on the rupture area, we relocate the aftershocks, using a relative location method (Cleveland & Ammon, 2013), based on cross-correlation of surface waves. Finally we discuss the implications of our results.
The 2002 earthquake is anomalous in the sense that it produced very small accelerations for its size (Iglesias et al 2003) and it is one of the earthquakes with longest duration relative to its magnitude recorded globally in the last 40 years (Duputel et al, 2013). Events of this type are particularly hazardous because they produce relatively large tsunamis (Kanamori, 1972) and small ground motions for their size, so they may be mistaken for smaller events by people near the coast, who may not prepare for the large tsunami. As near trench earthquakes are relatively rare, and due to their destruction potential, it is important to study in detail the few recorded events of this type.
The extent of the rupture area of the 2002 earthquake, is key to understanding the seismogenic potential of the Guerrero Gap. Often the rupture area of an earthquake is estimated by the extent of the aftershock area. However, locating earthquakes near the trench is difficult, due to their emerging P-waves and as they occur outside of the network of observation. In this study we calculate the duration of the 2002 earthquake by observations of far-field records. We use the difference in time between the first and last coherent signals in the peculiar P wavetrain of event, observed to conclude that the rupture had a duration and along strike length of approximately 56s and 60 km, respectively. The rupture propagated to the north-west with a rupture velocity of 1 km/s. To put further constraints on the rupture area, we relocate the aftershocks, using a relative location method (Cleveland & Ammon, 2013), based on cross-correlation of surface waves. Finally we discuss the implications of our results.