Constraining the Source of the Mw 8.1 Chiapas, Mexico Earthquake of 8 September 2017 Using Teleseismic and Tsunami Observations

El reciente temblor de Oaxaca, México (Ms = 7.8) es de especial interés pues se localiza dentro de un tramo de quietud ("gap") sísmica determinado previamente. El evento generó ondas Rayleigh y Love múltiples de periodo largo (100-200 seg.), que fueron bien registradas por la red WWSSN. Estos datos, junto con datos del primer movimiento de las ondas P, fueron usados para restringir el mecanismo focal. Los resultados indican un mecanismo focal de tipo de falla inversa y oblicua consistente con la subducción de la placa de Cocos según una dirección noreste bajo México (buzamientoâ‰ƒ14°, rumboâ‰ƒN90°W, deslizamiento â‰ƒ+54°); por lo tanto, este evento es ciertamente del tipo anticipado por Obtake, Matumoto y Latham (1977). A pesar de su gran tamaño, con momento sísmico Moâ‰ƒ 3.2 x 10 27dinas-cm, las ondas internas indican una fuente extremadamente simple dentro del rango de periodos de los sismógrafos de periodo largo de la red WWSSN. Esto fue verificado calculando sismogramas sintéticos para la forma de las ondas internas; se utilizo una fuente elemental y el mecanismo mencionado. Este tipo de simplicidad de las ondas internas para temblores fuertes de tipo subducción ha sido observado en otras áreas, especialmente en las Islas Salomón (Lay y Kanamori, 1978) y por lo tanto constituye una característica importante del modo de liberación de la energía elástica a lo largo de algunas zonas de subducción.

Download Full-text

Health aspects of the Mexico earthquake - 19th September 1985*

Disasters ◽

10.1111/j.1467-7717.1986.tb00579.x ◽

1986 ◽

Vol 10 (2) ◽

pp. 141-149 ◽

Cited By ~ 8

Author(s):

Jose Luis Zeballos

Keyword(s):

Mexico Earthquake

Download Full-text

A Source and Wave Propagation Study of the Copalillo, Mexico, Earthquake of 21 July 2000 (Mw 5.9): Implications for Seismic Hazard in Mexico City from Inslab Earthquakes

Bulletin of the Seismological Society of America ◽

10.1785/0120010144 ◽

2002 ◽

Vol 92 (3) ◽

pp. 1060-1071 ◽

Cited By ~ 12

Author(s):

A. Iglesias

Keyword(s):

Wave Propagation ◽

Seismic Hazard ◽

Mexico City ◽

Mexico Earthquake

Download Full-text

The 14 September 1995 (M = 7.3) Copala, Mexico, earthquake: A source study using teleseismic, regional, and local data

Bulletin of the Seismological Society of America ◽

10.1785/bssa0870040999 ◽

1997 ◽

Vol 87 (4) ◽

pp. 999-1010

Author(s):

F. Courboulex ◽

M. A. Santoyo ◽

J. F. Pacheco ◽

S. K. Singh

Keyword(s):

Time Window ◽

Time Function ◽

Source Process ◽

Source Time Function ◽

Nonlinear Method ◽

Local Data ◽

Plate Interface ◽

Linear Inversion ◽

Field Source ◽

Mexico Earthquake

Abstract We analyze source characteristics of the 14 September 1995, Copala, Mexico, earthquake (M = 7.3) using teleseismic, regional, and local seismograms. In the analysis of the teleseismic and the regional seismic waves, we apply the empirical Green's function (EGF) technique. The recording of an appropriate aftershock is taken as the EGF and is used to deconvolve the mainshock seismogram, thus obtaining an apparent far-field source-time function at each station. The deconvolution has been done using surface waves. For teleseismic data, we apply a spectral deconvolution method that enables us to obtain 37 apparent source-time functions (ASTFs) at 29 stations. In the analysis of the regional broadband seismograms, we use two different aftershocks as EGF, and the deconvolution is performed in the time domain with a nonlinear method, imposing a positivity constraint, and the best azimuth for the directivity vector is obtained through a grid-search approach. We also analyze two near-source accelerograms. The traces are inverted for the slip distribution over the fault plane by applying a linear inversion technique. With the aid of a time-window analysis, we obtain an independent estimation of the source-time function and a more detailed description of the source process. The analysis of the three datasets permits us to deduce the main characteristics of the source process. The rupture initiated at a depth of 16 km and propagated in two directions: updip along the plate interface toward 165° N and toward 70° N. The source duration was between 12 and 14 sec, with the maximum of energy release occurring 8 sec after the initiation of the rupture. The estimated rupture dimension of 35 × 45 km is about one-fourth of the aftershock area. The average dislocation over the fault was 1.4 m (with a maximum dislocation of 4.1 m located 10 km south of the hypocenter), which gives roughly 1 MPa as the average static stress drop.

Download Full-text