We introduce a new method to determine the magnitude of completeness M c and its uncertainty. Our method models the entire magnitude range (EMR method) consisting of the self-similar complete part of the frequency-magnitude distribution and the incomplete portion, thus providing a comprehensive seismicity model. We compare the EMR method with three existing techniques, finding that EMR shows a superior performance when applied to synthetic test cases or real data from regional and global earthquake catalogues. This method, however, is also the most computationally intensive. Accurate knowledge of M c is essential for many seismicity-based studies, and particularly for mapping out seismicity parameters such as the b-value of the Gutenberg-Richter relationship. By explicitly computing the uncertainties in M c using a bootstrap approach, we show that uncertainties in b-values are larger than traditionally assumed, especially when considering small sample sizes. As examples, we investigated temporal variations of M c for the 1992 Landers aftershock sequence and found that it was underestimated on average by 0.2 with former techniques. Mapping M c on a global scale, M c reveals considerable spatial variations for the Harvard Centroid Moment Tensor (CMT) (5.3 Յ M c Յ 6.0) and the International Seismological Centre (ISC) catalogue (4.3 Յ M c Յ 5.0).

The 2013 European Seismic Hazard Model (ESHM13) results from a community-based probabilistic seismic hazard assessment supported by the EU-FP7 project "Seismic Hazard Harmonization in Europe" (SHARE, 2009(SHARE, -2013. The ESHM13 is a consistent seismic hazard model for Europe and Turkey which overcomes the limitation of national borders and includes a through quantification of the uncertainties. It is the first completed regional effort contributing to the "Global Earthquake Model" initiative. It might serve as a reference model for various applications, from earthquake preparedness to earthquake risk mitigation strategies, including the update of the European seismic regulations for building design (Eurocode 8), and thus it is useful for future safety assessment and improvement of private and public buildings. Although its results constitute a reference for Europe, they do not replace the existing national design regulations that are in place for seismic design and construction of buildings. The ESHM13 represents a significant improvement compared to previous efforts as it is based on (1) the compilation of updated and harmonised versions of the databases required for probabilistic seismic hazard assessment, (2) the adoption of standard procedures and robust methods, especially for expert elicitation and consensus building among hundreds of European experts, (3) the multi-disciplinary input from all branches of earthquake science and engineering, (4) the direct involvement of the CEN/TC250/SC8 committee in defining output specifications relevant for Eurocode 8 and (5)

[1] During an Enhanced Geothermal System (EGS) experiment, fluid is injected at high pressure into crystalline rock, to enhance its permeability and thus create a reservoir from which geothermal heat can be extracted. The fracturing of the basement caused by these high pore-pressures is associated with microseismicity. However, the relationship between the magnitudes of these induced seismic events and the applied fluid injection rates, and thus pore-pressure, is unknown. Here we show how pore-pressure can be linked to the seismic frequency-magnitude distribution, described by its slope, the b-value. We evaluate the dataset of an EGS in Basel, Switzerland and compare the observed event-size distribution with the outcome of a minimalistic model of porepressure evolution that relates event-sizes to the differential stress s D . We observe that the decrease of b-values with increasing distance of the injection point is likely caused by a decrease in pore-pressure. This leads to an increase of the probability of a large magnitude event with distance and time.

The Southern California Seismic Network (SCSN) has produced the SCSN earthquake catalog from 1932 to the present, a period of more than 77 yrs. This catalog consists of phase picks, hypocenters, and magnitudes. We present the history of the SCSN and the evolution of the catalog, to facilitate user understanding of its limitations and strengths. Hypocenters and magnitudes have improved in quality with time, as the number of stations has increased gradually from 7 to ∼400 and the data acquisition and measuring procedures have become more sophisticated. The magnitude of completeness (M c ) of the network has improved from M c ∼3:25 in the early years to M c ∼1:8 at present, or better in the most densely instrumented areas. Mainshock-aftershock and swarm sequences and scattered individual background earthquakes characterize the seismicity of more than 470,000 events. The earthquake frequency-size distribution has an average b-value of ∼1:0, with M ≥ 6:0 events occurring approximately every 3 yrs. The three largest earthquakes recorded were 1952 M w 7.5 Kern County, 1992 M w 7.3 Landers, and 1999 M w 7

We present a new method for estimating earthquake detection probabilities that avoids assumptions about earthquake occurrence, for example, the event-size distribution, and uses only empirical data: phase data, station information, and network-specific attenuation relations. First, we determine the detection probability for each station as a function of magnitude and hypocentral distance, using data from past earthquakes. Second, we combine the detection probabilities of stations using a basic combinatoric procedure to determine the probability that a hypothetical earthquake with a given size and location could escape detection. Finally, we synthesize detection-probability maps for earthquakes of particular magnitudes and probability-based completeness maps. Because the method relies only on detection probabilities of stations, it can also be used to evaluate hypothetical additions or deletions of stations as well as scenario computations of a network crisis. The new approach has several advantages: completeness is analyzed as a function of network properties instead of earthquake samples; thus, no event-size distribution is assumed. Estimating completeness is becoming possible in regions of sparse data where methods based on parametric earthquake catalogs fail. We find that the catalog of the Southern California Seismic Network (SCSN) has, for most of the region, a lower magnitude of completeness than that computed using traditional techniques, although in some places traditional techniques provide lower estimates. The network reliably records earthquakes smaller than magnitude 1.0 in some places and 1.0 in the seismically active regions. However, it does not achieve the desired completeness of magnitude M L 1:8 everywhere in its authoritative region. A complete detection is achieved at M L 3:4 in the entire authoritative region; thus, at the boundaries, earthquakes as large as M L 3:3 might escape detection.