A non linear adaptive filter for digital data communication

This paper presents a recursive time-varying adaptation step algorithm for updating the linear and quadratic coefficients vectors of a second-order Volterra filter. Simulations are carried in an equalization setup to compare the performance of this algorithm with other variable step least mean square (LMS) algorithms. The obtained results show that this algorithm brings substantial increase in the adaptation speed while keeping simplicity of the conventional LMS algorithm

MAGNITUDE DEPENDENCE OF STRESS DROP: WHAT DOES THE OBSERVED MAGNITUDE SCALING OF GROUND-MOTIONS TELL US?

International audienceThe behavior of earthquake stress-drop magnitude scaling has been the topic of significant debate in the earthquake source community over the past two decades. Methodologies which have been adopted by a large number of source studies require corrections for source radiation pattern, path attenuation and site amplification that ultimately introduce large uncertainties for stress-drop estimates. In this study, we adopt a different strategy: we analyze directly the ground-motions (Y) and their dependencies with magnitude (M). We first use simple stochastic models (e.g. [1]) comprised of a [2, 3] source spectrum and various models of magnitude-dependent stress drop. We show that magnitude-dependent stress-drop and constant stress-drop models lead to different scaling of ground-motions (dlogY/dM) with frequency. Using the results of [4], we then analyze the magnitude dependency of NGA-West 2 ground-motions for source-site configurations where stress-drop is the key controlling factor of ground-motions (moderate distances and rock-sites). In addition, the use of a neural network method allows us to obtain fully record-driven evaluations of (dlogY/dM) with frequency both for simulated and observed records. The comparison between these observed and simulated (dlogY/dM) allows us to discuss the scaling of the stress-drop with magnitude. We do not observe strong differences of the magnitude scaling of ground-motions between mainshocks and aftershocks

MAGNITUDE DEPENDENCE OF STRESS DROP: WHAT DOES THE OBSERVED MAGNITUDE SCALING OF GROUND-MOTIONS TELL US?

International audienceThe behavior of earthquake stress-drop magnitude scaling has been the topic of significant debate in the earthquake source community over the past two decades. Methodologies which have been adopted by a large number of source studies require corrections for source radiation pattern, path attenuation and site amplification that ultimately introduce large uncertainties for stress-drop estimates. In this study, we adopt a different strategy: we analyze directly the ground-motions (Y) and their dependencies with magnitude (M). We first use simple stochastic models (e.g. [1]) comprised of a [2, 3] source spectrum and various models of magnitude-dependent stress drop. We show that magnitude-dependent stress-drop and constant stress-drop models lead to different scaling of ground-motions (dlogY/dM) with frequency. Using the results of [4], we then analyze the magnitude dependency of NGA-West 2 ground-motions for source-site configurations where stress-drop is the key controlling factor of ground-motions (moderate distances and rock-sites). In addition, the use of a neural network method allows us to obtain fully record-driven evaluations of (dlogY/dM) with frequency both for simulated and observed records. The comparison between these observed and simulated (dlogY/dM) allows us to discuss the scaling of the stress-drop with magnitude. We do not observe strong differences of the magnitude scaling of ground-motions between mainshocks and aftershocks