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La intrusión de magma debajo de la caldera de Long Valley confirmada por cambios temporales en la gravedad
1Department of Geophysics, Stanford University, Stanford, CA 94305, USA. U.S. Geological Survey, Menlo Park, CA 94025, USA.
Science (New York, N.Y.)
|September 25, 1999
Resumen
Las mediciones de la gravedad en Long Valley, California, muestran una disminución significativa, lo que indica la intrusión de magma. Este hallazgo excluye la expansión térmica o la presión hidrotermal como causas de elevación y actividad sísmica.
Área de la Ciencia:
- La geofísica es la geofísica.
- Volcanología Volcanología.
Sus antecedentes:
- La caldera de Long Valley, California, exhibe elevación de la superficie y sismicidad.
- Estudios anteriores sugirieron varias causas para estos fenómenos, incluida la expansión térmica y la actividad hidrotermal.
Objetivo del estudio:
- Para investigar los procesos subterráneos que impulsan la elevación y la sismicidad en Long Valley Caldera.
- Para determinar la naturaleza del material intruso responsable de los cambios en la gravedad.
Principales métodos:
- Se realizaron mediciones precisas de la gravedad relativa en 1982 y 1998.
- Se analizaron los datos de gravedad para detectar cambios y corregir los efectos conocidos como la elevación y las fluctuaciones del nivel freático.
Principales resultados:
- Se observó una disminución de la gravedad de hasta -107 +/- 6 microgals, centrada en la cúpula resurgente.
- Se detectó un cambio positivo en la gravedad residual de hasta 64 +/- 15 microgals después de las correcciones.
- La densidad del material intruso se estimó entre 2,7 x 10^3 y 4,1 x 10^3 kg/m^3.
Conclusiones:
- Los datos de gravedad apoyan fuertemente la intrusión de magma de silicato como la causa de la elevación y la sismicidad.
- La expansión térmica in situ o la presurización del sistema hidrotermal se excluyen como factores primarios.
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