ISC-GEM: Global Instrumental Earthquake Catalogue (1900–2009), II. Location and seismicity patterns

We present the final results of a two-year project sponsored by the Global Earthquake Model (GEM) Foundation. The ISC-GEM global catalogue consists of some 19 thousand instrumentally recorded, moderate to large earthquakes, spanning 110 years of seismicity. We relocated all events in the catalogue using a two-tier approach. The EHB location methodology (Engdahl et al., 1998) was applied first to obtain improved hypocentres with special focus on the depth determination. The locations were further refined in the next step by fixing the depths to those from the EHB analysis and applying the new International Seismological Centre (ISC) location algorithm (Bondár and Storchak, 2011) that reduces location bias by accounting for correlated travel-time prediction error structure. To facilitate the relocation effort, some one million seismic P and S wave arrival-time data were added to the ISC database for the period between 1904 and 1970, either from original station bulletins in the ISC archive or by digitizing the scanned images of the International Seismological Summary (ISS) bulletin (Villaseñor and Engdahl, 2005, 2007). Although no substantial amount of new phase data were acquired for the modern period (1964–2009), the number of phases used in the location has still increased by three millions, owing to fact that both the EHB and ISC locators use most well-recorded ak135 (Kennett et al., 1995) phases in the location. We show that the relocation effort yielded substantially improved locations, especially in the first half of the 20th century; we demonstrate significant improvements in focal depth estimates in subduction zones and other seismically active regions; and we show that the ISC-GEM catalogue provides an improved view of 110 years of global seismicity of the Earth. The ISC-GEM Global Instrumental Earthquake Catalogue represents the final product of one of the ten global components in the GEM program, and is available to researchers at the ISC (www.isc.ac.uk) website.Peer reviewe

Review of Synergic Meteor Observations: Linking the Results from Cameras, Ionosondes, Infrasound and Seismic Detectors

The joint evaluation of different meteor observation types supports a better understanding of both meteor phenomena and the terrestrial atmosphere. Two types of examples are presented in this work, linking ionospheric effects to specific meteors, with almost one-third of the meteors that emerged at high altitudes simultaneously recorded with an optical camera. Very few such observations have been realized as yet. With daytime fireballs, the recorded infrasound effect and the atmospheric blast produced shock-wave-related small earthquakes which were identified by a network of ground stations. An overview of these observational types highlights specific topics for which substantial improvements and discoveries are expected in the near future

The ISC-GEM Global Instrumental Earthquake Catalogue (1900-2009): Introduction

In this introductory article we give a general description of the ISC-GEM Global Instrumental Earthquake Catalogue (1900–2009). We also provide the background for four further articles that describe the effort in collecting and digitizing parametric earthquake bulletin data as well as the methodologies developed to compute homogeneous earthquake parameters. The result of the two and a half year project is a catalogue of approximately 20,000 large earthquakes covering 110 years with hypocentres and uncertainties computed using the same technique and velocity model. We show that the overall homogeneity of the main earthquake parameters in the catalogue was achieved despite changes in instrumentation and routine measurement practices concurrent with developments in instrumental seismology from almost a ground level to its current state. For each earthquake, MW magnitude values and uncertainties were computed either based on available estimates of seismic moment or using new empirical relationships between MW, MS and mb. Further important results of this project include the electronic availability of a considerable volume of seismic wave arrival time and amplitude measurements from early instrumental printed station bulletins. These newly recovered amplitude measurements provided a basis for computation of many previously unavailable MS magnitudes with uncertainties. In this article we describe why such a catalogue is required for a comprehensive assessment of global and regional seismic hazard. We also describe other potential uses of the catalogue in many other fields of Earth Sciences. We discuss the catalogue availability and lay out the plans of further development.Peer reviewe