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The static Coulomb stress hypothesis is a widely known physical mechanism for earthquake triggering, and thus a prime candidate for physics-based Operational Earthquake Forecasting (OEF). However, the forecast skill of Coulomb-based seismicity models remains controversial, especially in comparison to empirical statistical models. A previous evaluation by the Collaboratory for the Study of Earthquake Predictability (CSEP) concluded that a suite of Coulomb-based seismicity models were less informative than empirical models during the aftershock sequence of the 1992 M w 7.3 Landers, California, earthquake. Recently, a new generation of Coulomb-based and Coulomb/statistical hybrid models were developed that account better for uncertainties and secondary stress sources. Here, we report on the performance of this new suite of models in comparison to empirical Epidemic Type Aftershock Sequences (ETAS) models during the 2010-2012 Canterbury, New Zealand, earthquake sequence. Comprising the 2010 M 7.1 Darfield earthquake and three subsequent M ≥ 5.9 shocks (including the February 2011 Christchurch earthquake), this sequence provides a wealth of data (394 M ≥ 3.95 shocks). We assessed models over multiple forecast horizons (1-day, 1-month and 1-year, updated after M ≥ 5.9 shocks). The results demonstrate substantial improvements in the Coulomb-based models. Purely physics-based models have a performance comparable to the ETAS model, and the two Coulomb/statistical hybrids perform better or as well as the corresponding statistical model. On the other hand, an ETAS model with anisotropic (fault-based) aftershock zones is just as informative. These results provide encouraging evidence for the predictive power of Coulomb-based models. To assist with model development, we identify discrepancies between forecasts and observations.

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Abstract. Recent work has shown that disparate systems can be described as complex networks i.e. assemblies of nodes and links with nontrivial topological properties. Examples include technological, biological and social systems. Among them, earthquakes have been studied from this perspective. In the present work, we divide the Southern California region into cells of 0.1 • , and calculate the correlation of activity between them to create functional networks for that seismic area, in the same way that the brain activity is studied from the complex network perspective. We found that the network shows small world features.

The notion that three inbred strains of mice, i.e., C57BL/6J (C57), BALB/cByJ (BALB), and WB/ReJ (WB), which exhibit differential rates of age-related hearing loss (AHL), may also exhibit differential susceptibility to noise-induced hearing loss was tested by comparing the effects of sound overexposure on these strains. The aftereffects of noise overstimulation on the distortion-product otoacoustic emissions (DPOAEs) of these three strains were compared and contrasted to those for the CBA/CaJ (CBA) strain, which does not show changes in hearing threshold sensitivity up to 15 months of age. Two cohorts of mice, one at 2.5 and the other at 6 months of age, were first exposed to a tonal overstimulation paradigm, were allowed to recover, and then were later re-exposed to an octave band noise (OBN), at 3 or 7 months of age, respectively. The two sound exposure episodes were designed to produce either a temporary (tonal exposure) or permanent (OBN exposure) reduction in the levels of the 2f1 - f2 DPOAE in the WB strain, which exhibited the fastest rate of AHL. Although the tonal paradigm resulted in a temporary decrease in DPOAE levels for all strains at both ages, the 2.5-month BALBs showed the greatest susceptibility to this overexposure, while the 2.5-month WBs exhibited the least effects on DPOAEs. At the older age of 6 months, tonal overexposure produced essentially the same reduction in DPOAE levels for all four strains. In addition, there were no differences noted between CBAs and C57s, at either of the two ages. The OBN paradigm resulted in a permanent decrease in DPOAE levels in all the strains exhibiting early AHL, i.e., the C57, BALB, and WB mice, for frequencies about one-half to an octave higher than the exposure frequency, regardless of age. In contrast, the CBA strain was not significantly affected by the OBN overexposure.

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