1. The ISC-GEM Global Instrumental Earthquake Catalogue: an update
D. Di Giacomo, Bob Engdhal, D.A. Storchak and J. Harris
ESC 2016, Trieste, Session 16 1

2. Background www.isc.ac.uk/iscgem/
The ISC and a Team of International Experts released in January 2013 the ISC-GEM catalogue ( ), which provides basic earthquake parameters (location, moment magnitude, and, if available, moment tensor) along with corresponding uncertainties. This product is unique since it lists parameters obtained using the same techniques (to the largest extent possible) throughout the last 100+ years of instrumental seismology. It is available as CSV file (both main and supplementary catalogues) and also as KMZ (see Download & Legal). or

3. Background www.isc.ac.uk/iscgem/
In 2013 a short paper was published on SRL to announce the release of the ISC-GEM Catalogue, whereas in a PEPI special volume we describe in detail the various tasks accomplished to produce the catalogue:
Data collection
Relocation
Magnitude re-assessment
Bibliographic search of reliable seismic moments for events before 1976 (i.e., pre-GCMT) or

4. Phase and Amplitude Data Collection
Body/Surface Wave Amplitudes
Body Wave Arrival Times
Period
~10,000
~1,000,000
Quality station bulletins
DIGITALLY NOT AVAILABLE BEFORE THIS PROJECT
DIGITALLY AVAILABLE, ISC database
Major Sources of Phase Data:
Gutenberg Notepads ( ) and BAAS ( )
ISS Bulletins ( ) 4

5. Adding amplitudes from historical seismological bulletin
1906 San Francisco earthquake report from Göttingen (Germany) station bulletin.
The same report stored in digital format in the ISC database. Period and amplitude data finally available for magnitude recomputation.

6. Data Collection before extension started
In order to produce the ISC-GEM catalogue, we digitized a multitude of sources of parametric seismological data to facilitate location and magnitude re-computation for earthquakes before 1960.
The parametric data collected in this project will be useful for any future study for earthquakes occurred before 1964
Scans of the processed bulletins are available in PDF at SISMOS website:
Di Giacomo et al., PEPI 2015a
Add bullet on the data collection, stress more all of them

7. Location improvements
More details in Bondár et al., PEPI 2015

8. Improvements in magnitude, especially Ms
ISC-GEM recomputed Ms
Ms from Abe’s catalogue
More details in Di Giacomo et al., PEPI 2015b

9. Summary of the ISC-GEM catalogue before extension started
Given the time and resources in the project we processed only selected earthquakes using time-variable cut-off magnitudes:
M ≥ 7.5 up to 1917 (plus significant quakes in continental regions with M ≥ 6.5);
M ≥ 6.25 between 1918 and 1959;
M > 5.5 from 1960 onwards.
~19,000 earthquakes were listed in the catalogue first release
Modified from Di Giacomo et al. (2015b)

10. Extension project The work is planned for 4 years;
Large number of earthquakes below ~6.2 is to be added before 1960;
Also current years (post 2009) to be added.
Data for recent years is taken from the ISC Bulletin, whereas for earthquakes before 1960 we need to digitise the relevant data for relocation and magnitude re-computation

11. First year extension: 1950-1959
Number of ISS events in the 1950s
Year
Number of earthquakes relocated
1950
438
1951
469
1952
560
1953
352
1954
316
1955
299
1956
311
1957
355
1958
530
1959
526
Totals
4156
Box-and-whisker plot of the location differences before and after the ISC-GEM relocations in each year.
Box-and-whisker plot of the depth differences before and after the ISC-GEM relocations in each year.

12. First year extension: events with re-computed MS in the 1950s
Many ISS earthquakes in the 1950s fall below the ISC-GEM cut-off magnitude of 5.5, but rather than excluding completely those events we list them in the Supplementary Catalogue
Timeline of the re-computed MS in the 1950s

13. Second year extension: 1935-1949
Number of ISS events in between 1935 and 1949
Year
Number of earthquakes relocated
1935
253
1936
260
1937
246
1938
302
1939
235
1940
233
1941
204
1942
184
1943
287
1944
228
1945
295
1946
388
1947
387
1948
441
1949
460
Totals
4403
~2800 ISS pages have been edited and proof-read during this year… All ISS data now digitized!!
Box-and-whisker plot of the location differences before and after the ISC-GEM relocations in each year.
Box-and-whisker plot of the depth differences before and after the ISC-GEM relocations in each year.

14. Second year extension: events with re-computed MS during 1935-1949
Many ISS earthquakes during fall below the ISC-GEM cut-off magnitude of 5.5, but rather than excluding completely those events we list them in the Supplementary Catalogue
Timeline of the re-computed MS during

15. More “amplitude” stations added in the extension project
Thanks to additional bulletins collected from BGS, Uni-Strasbourg, GFU Prague, Ambraseys personal collection, RAS Obninsk and others we have been able to add many more stations compared to the first catalogue release.

16. Earthquakes already processed now with more MS stations
Maps of the “amplitude” stations added during the second year extension. The data added does not regard only earthquakes not processed before but also the ones already ion the ISC-GEM catalogue
The increase in the NSTA contributing to the event MS is quite significant: whilst 42% of the original MS was obtained from NSTA ≤ 5, for the revised MS this percentage drops to ~5%. In addition, the added amplitude data also allowed us to gain 36 more MS values.

17. Summary after the second year extension
Before extension started
With extension during ,
Add bullet on the data collection, stress more all of them
ESC 2016, Trieste, Session 16

18. ISC Members and Sponsors
67 Institutions in 49 countries make annual membership subscriptions.
12 international, public or commercial entities sponsor individual ISC projects:
ISC-GEM Catalogue
CTBTO Link to ISC database
ISC Event Bibliography
Aon Benfield,
Lloyd’s,
Guy Carpenter,
Catlin.
International Station Registry