11 The Global Earthquake Activity Rate (GEAR1) seismicity model uses an optimized combination 12 of geodetic strain rates, hypotheses about converting strain rates to seismicity rates from plate 13 tectonics, and earthquake-catalog data to estimate global m w ≥ 5 . 767 shallow ( ≤ 70 km) seismicity 14 rates. It comprises two parent models: a strain rate-based model, and a smoothed-seismicity 15 based model. The GEAR1 model was retrospectively evaluated and calibrated using earthquake 16 data from 2005–2012, resulting in a preferred log-linear, multiplicative combination of the parent 17 forecasts. Since October 1, 2015, the GEAR1 model has undergone prospective evaluation within 18 the Collaboratory for the Study of Earthquake Predictability (CSEP) testing center. 19 We present initial prospective forecast test results for the GEAR1 model, its tectonic and 20 seismicity components, and for the first iteration of the strain rate-based model, during the period 21 October 1, 2015 to September 7, 2017. Observed earthquakes are consistent with the GEAR1 22 forecast, supporting a near-even contribution from geodetic strain rates and smoothed seismicity in 23 constraining long-term global shallow earthquake rates. Comparative test results likewise support 24

The Collaboratory for the Study of Earthquake Predictability (CSEP) is a global cyberinfrastructure for prospective evaluations of earthquake forecast models and prediction algorithms. CSEP's goals are to improve our understanding of earthquake predictability, advance forecasting model development, test key scientific hypotheses and their predictive power, and improve seismic hazard assessments. Since its inception in California in 2007, the global CSEP collaboration has been conducting forecast experiments in a variety of tectonic settings and at a global scale and now operates four testing centers on four continents to automatically and objectively evaluate models against prospective data. These experiments have provided a multitude of results that are informing operational earthquake forecasting systems and seismic hazard models, and they have provided new and, sometimes, surprising insights into the predictability of earthquakes and spurned model improvements. CSEP has also conducted pilot studies to evaluate ground-motion and hazard models. Here, we report on selected achievements from a decade of CSEP, and we present our priorities for future activities.

We present highlights from the first decade of operation of the New Zealand Earthquake Forecast Testing Center of the Collaboratory for the Study of Earthquake Predictability (CSEP). Most results are based on reprocessing using the best available catalog, because the testing center did not consistently capture the complete real-time catalog. Tests of models with daily updating show that aftershock models incorporating Omori-Utsu decay can outperform long-term smoothed seismicity models with probability gains up to 1000 during major aftershock sequences. Tests of models with 3-month updating show that several models with every earthquake a precursor according to scale (EEPAS) model, incorporating the precursory scale increase phenomenon and without Omori-Utsu decay, and the double-branching model, with both Omori-Utsu and exponential decay in time, outperformed a regularly updated smoothed seismicity model. In tests of 5-yr models over 10 yrs without updating, a smoothed seismicity model outperformed the earthquake source model of the New Zealand National Seismic Hazard Model. The performance of 3-month and 5-yr models was strongly affected by the Canterbury earthquake sequence, which occurred in a region of previously low seismicity. Smoothed seismicity models were shown to perform better with more frequent updating. CSEP models were a useful resource for the development of hybrid time-varying models for practical forecasting after major earthquakes in the Canterbury and Kaikoura regions.

1 The static Coulomb stress hypothesis is a widely known physical mechanism for 2 earthquake triggering, and thus a prime candidate for physics-based Operational Earth3 quake Forecasting (OEF). However, the forecast skill of Coulomb-based seismicity mod4 els remains controversial, especially in comparison to empirical statistical models. A 5 previous evaluation by the Collaboratory for the Study of Earthquake Predictabil6 ity (CSEP) concluded that a suite of Coulomb-based seismicity models were less in7 formative than empirical models during the aftershock sequence of the 1992 Mw7.3 8 Landers, California, earthquake. Recently, a new generation of Coulomb-based and 9 Coulomb/statistical hybrid models were developed that account better for uncertainties 10 and secondary stress sources. Here, we report on the performance of this new suite of 11 models in comparison to empirical Epidemic Type Aftershock Sequences (ETAS) mod12 els during the 2010-2012 Canterbury, New Zealand, earthquake sequence. Comprising 13 the 2010 M7.1 Darfield earthquake and three subsequent M ≥ 5.9 shocks (including 14 the February 2011 Christchurch earthquake), this sequence provides a wealth of data 15 (394 M ≥ 3.95 shocks). We assessed models over multiple forecast horizons (1-day, 16 1-month and 1-year, updated after M ≥ 5.9 shocks). The results demonstrate substan17 tial improvements in the Coulomb-based models. Purely physics-based models have a 18 performance comparable to the ETAS model, and the two Coulomb/statistical hybrids 19 perform better or as well as the corresponding statistical model. On the other hand, 20 an ETAS model with anisotropic (fault-based) aftershock zones is just as informative. 21 These results provide encouraging evidence for the predictive power of Coulomb-based 22 models. To assist with model development, we identify discrepancies between forecasts 23 and observations. 24

The Collaboratory for the Study of Earthquake Predictability (CSEP) aims to advance earthquake research by rigorous testing of earthquake forecast hypotheses. As in other disciplines, such hypothesis testing requires carefully designed experiments that meet certain requirements: they should be reproducible, fully transparent, and conducted within a controlled environment. CSEP has begun building infrastructure for conducting such rigorous earthquake forecasting experiments. Because past earthquake prediction experiments often have been controversial, CSEP testing centers—the secure, controlled computational environments within which experiments are conducted—have been designed to address particular issues related to transparency and exact reproducibility. Moreover, CSEP fosters collaboration among scientists developing earthquake forecast models, and the testing center concept allows multiple concurrent predictability experiments. In this paper, we share our perspective on computational earthquake science by presenting the design principles, organizational structure, and implementation details of CSEP testing centers. We describe ongoing forecast experiments in different testing regions and some of the implementation challenges encountered. We also describe the collaboration tools used for multinational software development and regional presentation websites. The need for common data exchange formats is discussed, as are potential avenues of future research within CSEP testing centers. Copyright © 2009 John Wiley & Sons, Ltd.