The International Seismological Centre Global Earthquake Model (ISC–GEM) Global Instrumental Earthquake Catalogue (1900–2009) is the result of a special effort to substantially extend and improve currently existing global catalogs to serve the requirements of specific user groups who assess and model seismic hazard and risk. The data from the ISC–GEM Catalogue would be used worldwide yet will prove absolutely essential in those regions where a high seismicity level strongly correlates with a high population density (Fig. 1 ). The Catalogue is also expected to have a multidisciplinary use in a wide range of studies such as global seismicity assessment, tectonics, as well as the rapid determination of seismic hazard. Because of the large volume of digitized seismic traveltime and amplitude data generated during this project, we expect the Catalogue to be useful in studies of the inner structure of the Earth as well as in nuclear monitoring research. This global catalog was also designed to serve as a reference to be used for calibration purposes by those compiling regional seismicity catalogs that contain events of much smaller magnitudes. This will guarantee that the catalogs prepared by other teams for different regions will contain comparable earthquake locations and magnitude parameters, especially in border areas. The work on the Catalogue was funded by the GEM Foundation as part of the five Global Hazard Components and is a result of a 27-month-long project. This project was led by the ISC and performed by the team of international experts in accordance with the requirements of the Scientific Board of GEM and following recommendations of the International Association of Seismology and Physics of the Earth’s Interior (IASPEI ) observers. Further, eight IT, administrative, and technical staff at the ISC worked on this project. Details can be found in the Acknowledgments.Peer Reviewe

We have studied faulting associated with bending of the incoming oceanic plate along segments of Middle America and Chile subduction zones and its relationship to intermediate‐depth intraslab seismicity and slab geometry. Multibeam bathymetry shows that bending‐related faulting forms patterns made of sets of faults with orientations ranging from parallel to almost perpendicular to the trench axis. These fault patterns may change along a single subduction zone within along‐strike distances of several hundred kilometers or less. Where available, near‐trench intraplate earthquakes show normal‐fault focal mechanisms consistent with mapped bending‐related normal faults. The strike of bending‐related faults in the incoming oceanic plate is remarkably similar to the strike of the nodal planes of intermediate‐depth earthquakes for each segment of the study areas. This similarity in strike is observed even for faults oriented very oblique to the trench and slab strikes. Thus, in the studied subduction zones, results strongly support that many intraslab earthquakes do not occur along the planes of maximum shear within the slab and that much intermediate‐depth seismicity occurs by reactivation of faults formed by plate bending near the trench. Furthermore, a qualitative relationship between trench faulting and intraslab seismicity is indicated by segments of the incoming plate with pervasive bend‐faulting that correspond to segments of the slabs with higher intermediate‐depth seismicity.

We develop and apply a full waveform inversion method that incorporates seismic data on a wide range of spatio-temporal scales, thereby constraining the details of both crustal and upper-mantle structure. This is intended to further our understanding of crust–mantle interactions that shape the nature of plate tectonics, and to be a step towards improved tomographic models of strongly scale-dependent earth properties, such as attenuation and anisotropy. The inversion for detailed regional earth structure consistently embedded within a large-scale model requires locally refined numerical meshes that allow us to (1) model regional wave propagation at high frequencies, and (2) capture the inferred fine-scale heterogeneities. The smallest local grid spacing sets the upper bound of the largest possible time step used to iteratively advance the seismic wave field. This limitation leads to extreme computational costs in the presence of fine-scale structure, and it inhibits the construction of full waveform tomographic models that describe earth structure on multiple scales. To reduce computational requirements to a feasible level, we design a multigrid approach based on the decomposition of a multiscale earth model with widely varying grid spacings into a family of single-scale models where the grid spacing is approximately uniform. Each of the single-scale models contains a tractable number of grid points, which ensures computational efficiency. The multi-to-single-scale decomposition is the foundation of iterative, gradient-based optimization schemes that simultaneously and consistently invert data on all scales for one multi-scale model. We demonstrate the applicability of our method in a full waveform inversion for Eurasia, with a special focus on Anatolia where coverage is particularly dense. Continental-scale structure is constrained by complete seismic waveforms in the 30–200 s period range. In addition to the well-known structural elements of the Eurasian mantle, our model reveals a variety of subtle features, such as the Armorican Massif, the Rhine Graben and the Massif Central. Anatolia is covered by waveforms with 8–200 s period, meaning that the details of both crustal and mantle structure are resolved consistently. The final model contains numerous previously undiscovered structures, including the extension-related updoming of lower-crustal material beneath the Menderes Massif in western Anatolia. Furthermore, the final model for the Anatolian region confirms estimates of crustal depth from receiver function analysis, and it accurately explains cross-correlations of ambient seismic noise at 10 s period that have not been used in the tomographic inversion. This provides strong independent evidence that detailed 3-D structure is well resolved.