Advances in the assessment of the local seismological Magnitude scale ML for Venezuela

 

 

Raquel Vásquez Stanescu

Fundación Venezolana de Investigaciones Sismológicas

Publicado en: Saber: Revista Multidisciplinaria del Consejo de Investigacion, (29).

Resumen:

In this study we determined local magnitude scales ML for Venezuela for vertical (Z) and horizontal seismological components (N-S y E-W), respectively, recorded by the National Seismological Network. We measured 636 vertical and horizontal peak amplitude data for 50 inland earthquakes which occurred between 2006 and 2012, that were recorded by 35 broadband stations of the National Seismological Network. The focal depths were shallow (up to 25 km) and the magnitude range was from 3.4 to 5.7 Mw. We found a good correlation between maximum amplitudes on the vertical component and those on the horizontal component. The average of the ratio of the horizontal component amplitude to the vertical component amplitude was 1.7. The local magnitude coefficients for geometrical spreading and anelastic attenuation obtained by linear inversion were 1.031 and 0.00116 for the vertical component, and 1.306 and 0.00075 for the horizontal component, respectively. The magnitude residuals calculated for the local magnitude formulas obtained in this study did not show significant dependence on the hypocentral distance. We compared local magnitudes for both components and found that the local magnitude for the vertical component was smaller than that for the horizontal component by about 0.2 in the magnitude range from 3.2 to 5.5. The distance corrections for Venezuela at the distance range larger than 100 km are lower than that for Southern California, which is adopted for the International Association of Seismology and Physics of the Earth's Interior (IASPEI) standard formula.

KEY WORDS: National Seismological Network, anelastic attenuation, geometrical spreading.

Disponible en: https://drive.google.com/file/d/1BdiJqtlcwGC4Rc90fzWIDdQlTmtS7eg9/view?usp=sharing