The empirical Green function (EGF) model, which is used in this paper for the analysis of the waveforms of low-energy earthquakes, consists in assuming that the propagating medium and the recording instrument can be treated as a linear system and that the impulse response function of the system can be approximated by the waveform of a very small earthquake. The deconvolution of the Green function event from the waveform of a larger one, located at approximately the same position, provides information about the source time function (STF) of the latter. Linear inversion methods do not yield satisfactory estimations of the STF which must be positive and causal. Moreover, an estimate of the duration (support) of the STF should be desirable. In this paper we apply to this problem the so-called projected Landweber method, which is an iterative nonlinear method allowing for the introduction of constraints on the solution. The implementation of the method is easy and efficient. We first validate the method by means of synthetic data, generated by the use of waveforms of a seismic swarm that occurred in the Ligurian Alps (north-western Italy) during July 1993. Then, taking into account the indications provided by the simulations, the method has been applied to the inversion of real data, yielding satisfactory results also in the case of quite complex events.
[1] In this study we present new high-resolution, regional-scale, Vp and Vp/Vs models of the northern-central Apennines along with accurate 3-D locations of a large set of local earthquakes. The main velocity anomalies are consistent with the surface geology in the shallow layers and present evidence for fluids stored within the basement at greater depths beneath the extensional belt. The Adria and Tyrrhenian mantle are defined by positive velocity anomalies below 30 km depth, while a low-Vp, high-Vp/Vs region in between indicates the existence of a hydrated wedge. The results yield new constraints on active processes in the Apennines and more generally envisage the evolution of a postcollisional belt. Velocity anomalies and earthquakes are consistent with a complex system of delamination and sinking of the Adria continental lithosphere, with the peeling of the crust identified by intermediate-depth seismicity. Change of seismicity and structural patterns along the belt indicates that this tectonic process is diachronous and that fluids, released by sunken lithosphere, are stored within the crust, conditioning the occurrence of seismicity and the onset of extension.Citation: Carannante, S., G. Monachesi, M. Cattaneo, A. Amato, and C. Chiarabba (2013), Deep structure and tectonics of the northern-central Apennines as seen by regional-scale tomography and 3-D located earthquakes,
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.