1. Extending the ISC-GEM Global Instrumental Catalogue
D. Di Giacomo, Bob Engdhal, D.A. Storchak, A. Villaseñor and J. Harris 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 110 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.
To process large earthquakes occurred in the last 100+ years we first had to digitize the necessary instrumental parametric data (hypocenters, magnitudes, phase time arrivals, amplitude and periods of different phases, etc.) in order to apply the same modern techniques we use for current earthquakes also to past ones.
Modified from Di Giacomo et al. (2015b)
~19,000 earthquakes were listed in the catalogue first release

10. Extension plan 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. First year extension: earthquakes without re-computed magnitude in the 1950s
Spatial distribution of the relocated events in the 1950s without magnitude (listed in the Supplementary Catalogue)
Timeline of the relocated events in the 1950s without magnitude (listed in the Supplementary Catalogue)

14. Summary All ISC-GEM work is possible thanks to the support of
Before extension started
With extension in the 1950s,
Add bullet on the data collection, stress more all of them
All ISC-GEM work is possible thanks to the support of
and 62 ISC Members from 45 countries