Detailed Analysis of a Multiplet Earthquake Sequence

Thursday, 18 December 2014
Arturo Iglesias1, S.K. Singh1 and Víctor Hugo Garduño2, (1)UNAM National Autonomous University of Mexico, Mexico City, Mexico, (2)UMSNH Universidad Michoacana de San Nicolás de Hidalgo, Michoacan, Mexico
The Mexican National Seismological Service reported a sequence of four small earthquakes (2.5 < M < 3.0) occurring in Morelia, a city of 1,000,000, which is the capital city of Michoacán State.

A careful revision of the records from a three-component broad band station, located ~10 km far from the earthquakes, showed a sequence of 7 earthquakes in a period of about 36 hours. Waveforms are remarkably similar between them and they may be considered as a “multiplet”. In this work, we use the records from the broad-band station and a coda wave interferometry based methodology to obtain the relative distance between pair of events.

The 21 inter-event distances obtained are considered as over-determined system for the relative positions between events. A non-linear damped scheme is used to solve the over-determined system and to obtain the spatial distribution of the 7 earthquakes.

Results show (1) distances between events are < 200 m, and (2) the sequence has an approximate linear distribution.