The ISC-GEM Global Instrumental Earthquake Catalogue 2018 - International Seismological Centre

Version 5.0 & 5.1 of the ISC-GEM Catalogue is the result of the 4th year of the Extension Project that began in November 2014. We included earthquakes smaller than 7.5 during 1904-1919 from a multitude of sources that were not processed in the past. We also included earthquakes that occurred in 2014. For earthquakes during 1904-1919 we had to digitize a multitude of station data sources from the ISA BAAS, ISS etc. and amplitude-period data added from original station bulletins to re-assess the magnitudes (mostly MS). The procedures used to digitize the parametric data is described in Di Giacomo et al. (2015). We did not add any station data before 1904 (basically only stations belonging to the Milne network are available, see, e.g., Adams, 1989) and, consequently, we decided to drop from the ISC-GEM catalogue the ten pre‑1904 events listed before Version 5 and have the catalogue starting in 1904.

Version 5.0 adds 521 earthquakes that occurred in 2014 with magnitude 5.5 and above and 1,110 for the period 1904-1919. For the latter period, details of the extension are described in Di Giacomo et al. (2018, in preparation).

We collected stations bulletins from various sources that complemented significantly the original ISC inventory of station bulletins. On top of the extension work, therefore, we decided to add amplitude data from the newly available station's bulletins also for the earthquakes that were already available in the ISC-GEM catalogue to improve the re‑computed MS and, as a result, the Mw proxy. With the data newly available, we better constrained the MS for 146 earthquakes between 1904 and 1919 listed in previous versions by using more station magnitudes (e.g., 80% of the original MS was obtained from NSTA ≤ 10, for the updated MS this percentage drops to ~40%). Finally, we revised the hypocentre locations and/or magnitude of 7 earthquakes outside the period 1904-1919. Here we list in detail the changes affecting these events:

Evid = 16958009 has now a direct Mw = 7.1 following the paper by Pino et al. (2000);

Evid = 16958130, also known as the 1911 Kemin earthquake has an updated direct Mw = 8.0 following the recent paper of Kulikova and Krüger (2015). Also, the location has been updated after adding several phase readings; Evid = 912062: updated location (~125 km to the SW) after considering the effects of the earthquake outlined in Ruiz and Madariaga (2018);

Evid = 908523: update location (~40 toward NNW and depth changed from 15 to 65 km) after Paolo Harabaglia (University of Basilicata, Italy) pointed out the need of improving the hypocentre;

Evid = 907513, also known as the 1930 Irpinia earthquake has now a direct Mw = 6.64 following the paper of Pino et al. (2008);

Evid = 902493 has an updated location which fits better the tsunami generation; we thank Jonathan Griffin from Geoscience Australia for his enquiry on the location of this event and following discussions;

Evid = 722344, also known as the 1975 Hilo, Hawaii, earthquake has an updated direct Mw = 7.7 following the more recent paper of Nettles and Ekström (2004) instead of Kawakatsu (1989); Deleted event 650848 as part of the review done in the Rebuild project (Storchack et al., 2017);

Version 5.1, Added 17 earthquakes between 1933 and 1949, all but one from the Gutenberg and Richter catalogue; these events are undetermined shocks in the ISS and with station data not in tabulated form; to relocate and reassess the magnitude of these events we digitized and integrated parametric station data from the ISS, Gutenberg notepads, individual station bulletins and BCIS; twelve of these earthquakes (evid 16963127, 16963144, 16963678, 16964661, 16964943, 16965068, 16965286, 16965324, 16966074, 16966380, 16966502, 16967106) are listed in the Main catalogue and are all shallow in the magnitude range 6.0 to 6.4 (many occurring in mid-oceanic ridges); the remaining five earthquakes have poor location and/or magnitude and are listed in the Supplementary catalogue (evid 16963156, 16964624, 16965441, 16965882, 16965899);

The direct Mw and M0 for evid = 16957859 and 16957865 (Tsetserleg and Bolnay 1905 great earthquakes in Mongolia, respectively) sourced from Schlupp and Cisternas (2007) are now correctly associated (in V4 the Mw and M0 values were swapped). Thus the Tsetserleg (evid = 16957859) and Bolnay (evid = 16957865) earthquakes have Mw= 7.95±0.2 and earthquake 8.33±0.2, respectively. Also, the seismic moment values have been updated accordingly. We thank Nobuo Hamada (formerly JMA) for pointing out the error; Improved location and magnitude for the 1905-11-08 earthquake (Aegean Sea, Greece, evid = 16957878). The epicentre moved about 122 km N-NE (near Mt Athos peninsula) from the previous location, whereas the proxy Mw = 7.24 is now based on MS from five stations (instead of two in previous catalogue versions). The small uncertainty of the updated magnitude allowed us to move the event from the Supplementary to the Main Catalogue; Update location (about 270 km to the E) for evid 911802; also the magnitude has been improved since the Mw proxy is now based on MS from eight stations instead of five; Evid = 909805 is now listed in the Supplementary Catalogue as its location quality flag has been updated to D; we thank Paolo Harabaglia from the University of Basilicata (Italy) for pointing out the large error ellipse semi-major axis for this event; Evid = 899720 now has a proxy Mw = 6.3 based on our re-computed MS after adding surface wave amplitudes from station HYD, India (MS from two stations, SVE and TIF, was not accepted in previous versions); the event is now listed in the Main Catalogue;

Updated the seismic moment M0 from the bibliographic search for evid = 828259 and 761994. In both cases, the seismic moments from Richardson and Solomon (1977) were inserted with typos (1.12E+19 and 6.6E+18 Nm instead of 8.2E+18 and 6.4E+18 Nm for evid 828259 and 761194, respectively). Also, the source reference for the seismic moment for evid = 828259 is now Singh et al. (1975) instead of Richardson and Solomon (1977). For both earthquakes the small variations in M0 does not significantly change the moment magnitude Mw (for evid = 828259 Mw changes from 6.6 to 6.54);

Replaced the Mw=6.5+/-0.2 from the bibliographic search for evid = 713088 with a proxy Mw=6.09+/-0.24 based on our re-computed mb;

Minor changes due to the review was done in the Rebuild project (Storchak et al., 2017): For close events 684685 and 684686 we have moved the GCMT solution from 684685 to 684686; evid = 684685 is now listed in the Supplementary Catalogue as its Mw proxy based on our re-computed mb has high uncertainty;

Replaced evid = 805431 (event previously in the Supplementary Catalogue) with evid = 805429 (listed in the Main Catalogue);

Replaced evid = 856064 with evid = 856063.