Abstract
Abstract. The earthquake anomalies associated with the 6 April 2009 Mw 6.3 L'Aquila earthquake have been widely reported. Nevertheless, the reported anomalies have not been so far synergically analyzed to interpret or prove the potential lithosphere–coversphere–atmosphere coupling (LCAC) process. Previous studies on b value (a seismicity parameter from Gutenberg–Richter law) are also insufficient. In this work, the spatiotemporal evolution of several hydrothermal parameters related to the coversphere and atmosphere, including soil moisture, soil temperature, near-surface air temperature, and precipitable water, was comprehensively investigated. Air temperature and atmospheric aerosol were also statistically analyzed in time series with ground observations. An abnormal enhancement of aerosol occurred on 30 March 2009 and thus proved quasi-synchronous anomalies among the hydrothermal parameters from 29 to 31 March in particular places geo-related to tectonic thrusts and local topography. The three-dimensional (3-D) visualization analysis of b value revealed that regional stress accumulated to a high level, particularly in the L'Aquila basin and around regional large thrusts. Finally, the coupling effects of geospheres were discussed, and a conceptual LCAC mode was proposed to interpret the possible mechanisms of the multiple quasi-synchronous anomalies preceding the L'Aquila earthquake. Results indicate that CO2-rich fluids in deep crust might have played a significant role in the local LCAC process.
Highlights
The thermal anomalies occurring before large and hazardous earthquakes have been extensively observed from satellites or on the Earth’s surface
Four parameters related to the coversphere and atmosphere, namely, volumetric soil moisture level 1 (SML1) at 0–7 cm b.g.l., soil temperature level 1 (STL1) at 0–7 cm b.g.l., near-surface air temperature at a height of 2 m (TMP2m), and precipitable water of the entire atmosphere column (PWATclm), were analyzed in long-term intervals and within 2 months before and after the mainshock
The six-hourly values of the SML1 and STL1 parameters were 00:00, 06:00, 12:00, and 18:00 UTC every day according to ERA-Interim reanalysis dataset, which is a series of the latest global atmosphere reanalysis products produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) to replace the ERA-40
Summary
The thermal anomalies occurring before large and hazardous earthquakes have been extensively observed from satellites or on the Earth’s surface. A large number of the precursory anomalies of the 2009 L’Aquila earthquake were reported after the mainshock These anomalous parameters included thermal properties, electric and magnetic fields, ionospheric parameters, underground water, gas emission, crust stress, and seismicity From retrospective analyses of data collected prior to this earthquake, we attempt to discuss the geosphere coupling process and propose a model for interpreting the LCAC effects with the support of previous geophysical researches
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