ISC-GEM Global Instrumental Earthquake Catalogue (1900-2009)

This report describes the ISC-GEM Global Instrumental Earthquake Catalogue (1900-2009) created on the request and with sponsorship from the GEM Foundation. * The ISC-GEM Global Instrumental Earthquake Catalogue (1900-2009) is a major step forward on the way to improve characterization of spatial distribution of seismicity, magnitude frequency relation and maximum magnitudes within the scope of GEM. * With a few exceptions, parameters of this catalogue are the result of computations based on the original reports of seismic stations and observatories. * We made every effort to use uniform location and magnitude determination procedures during the entire period of the catalogue: - In earthquake location, we used a combination of the EHB depth determination technique and the new ISC procedures that use a multitude of primary and secondary seismic phases from the IASPEI Seismic Phase List and the ak135 velocity model and take into account the correlated error structure. - In determination of earthquake magnitude, where possible, we used direct MW values from Global CMT project for the period 1976-2009. In addition, 1,127 high quality scientific papers have been processed to obtain directly measured values of M0 and MW for 970 large earthquakes during 1900-1979. In all other instances we computed MW proxy values based on our own determination of instrumental surface or body wave magnitudes using updated regression models. - It has to be noted that a computation of MW proxy values based on regressions from other types of magnitudes does not bring similarly reliable results as compared to a direct measurement of MW based on the original waveform analysis. It is, nevertheless, a necessary measure since the direct measurement of MW using historical analogue waveforms on a global scale is beyond the scope of this project. * A number of important additional benefits have been achieved during this project: - The entire ISC collection of historical paper-based seismic station bulletins was reviewed, indexed and catalogued for further works. Indexes of similar collections at USGS/Berkeley were used in filling the gaps in the ISC collection. - A large number of seismic phase arrival times, body and surface wave amplitude measurements have been made electronically available on a global scale that have never been available on a global scale prior to this project. - A large number of more accurate network MS and mb magnitudes have been computed for large earthquakes that eit