Poster S101PS.02. D. Di Giacomo 1 , J. Harris 1 , A. Villaseñor 2 , D.A. Storchak 1 , E.R. Engdahl 3 , G. Ferrari 4 1 International Seismological Centre, Thatcham, UK, [email protected] 2 Institute of Earth Sciences Jaume Almera, ICTJA-CSIC, Barcelona, Spain
D. Di Giacomo1, J. Harris1, A. Villaseñor2, D.A. Storchak1, E.R. Engdahl3, G. Ferrari4
1International Seismological Centre, Thatcham, UK, [email protected]
2Institute of Earth Sciences Jaume Almera, ICTJA-CSIC, Barcelona, Spain
3University of Colorado at Boulder, USA
4Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Italy
As one of the global components of the Global Earthquake Model Foundation (GEM, http://www.globalquakemodel.org/), wecollected,digitizedandprocessedanunprecedentedamountofpaper-based early instrumentalseismologicalbulletins (stations or network) withfundamentalparametricdataforrelocatingandreassessingthemagnitudeofearthquakesthatoccurredintheinstrumentalperiodbetween1904and1970.Thiseffortwasnecessaryinordertoproduceanearthquakecataloguewithlocationsandmagnitudesashomogeneousaspossible.Theparametricdataobtainedandprocessedduringthisworkfillsalargegapinelectronicbulletindataavailability. The instrumental data collected is limited to earthquakes selected according to three cut-off magnitudes:
3) Amplitude-period data collection (1904-1970)
Added to the ISC database in a semi-automatic way using optical character recognition (OCR) methods. OCR techniques are applicable to ISS Bulletins thanks to a fairly stable format.
Intheperiod1918-1959~620,900 body‑wave arrival times for~850seismicstationsfromaroundtheworld were added.
A major drawback with the ISS and other data sources is the lack of the required data (e.g., amplitude, period and component information) for seismic phases useful for re‑computing classical magnitude scales such as MS and mb. In order to obtain magnitudes consistent with the relocated hypocentres, we needed to retrieve the necessary information from the early instrumental seismological bulletins.
Example scan of the ISS Bulletin: station data for an earthquake occurred the 1942-11-10.
Annual number of surface wave (black) and vertical component P-wave (gray) amplitude-period measurements manually entered from seismological bulletins.
A view of the ISC warehouse containing the original collection of early instrumental seismic station bulletins
Part of the ISS data was already convertedtodigitalform before thebeginningofthiswork:
a) example of station parametric data from Göttingen (Germany) of the 1906 San Francisco earthquake and b) the same data entered in the ISC database.
Map and timeline coverage for the seismic stations we added manually amplitude-period data for magnitude recomputation (see Poster S101PS.01).
Example scans of the hand‑written Gutenberg notepads: a) station data for an earthquake occurred the 1904-04-04 in Bulgaria and b) for two earthquakes occurred in the Hindu-Kush region in October 1908.
Manually added to the ISC database.
For67 largeearthquakes selected intheperiod1904-1912~1,900body‑wavearrivaltimesfor~100seismicstationsfromaroundtheworld were added.
JMA Bulletin data was digitally available and made available to the ISC by Professor Hamada. The early JMA bulletin is in a computer-readable format and it was, therefore, possible to parse it automatically. About 270,000 from about 230 stations were used in the ISC‑GEM relocation procedure.
Each vertical segment represents the earthquake origin time for which station parametric data was added. The effect of WWI and WWII are clearly seen on the timeline plot.
Overall amount of instrumental data gathered from different sources and used to produce the ISC-GEM catalogue, including modern period and data digitally available before this work (green colors).We consider the data added in this work a significant step forward on the way of improving any future study for earthquakes occurred in the early instrumental period.
These bulletins are the predecessors of the International Seismological Summary (ISS), and are available in good quality printed form
Manually added to the ISC database.
For45 largeearthquakes selected intheperiod1913-1917~3,800body‑wavearrivaltimesfor~100seismicstationsfromaroundtheworld were added.
Example scan of the BAAS bulletin: station data for an earthquake occurred the 1913-05-30.
Annual number of arrival times of P-wave (red) and S-wave type (blue) before 1960 collected from different. The annual number of P-wave (yellow) and S‑wave type (brown) manually added as part of the amplitude data entry task (described later) is also shown
Distribution of the stations for which phase data were added before 1960. Each station is colour-coded by total number of arrivals added before 1960.
BAAS (1913-1917). British Association for the Advancement of Science, Seismological Committee, quarterly issues.
ISS (1918-1963). International Seismological Summary, annual volumes.
Engdahl, E.R., and A. Villaseñor, 2002. Global Seismicity: 1900–1999, in W.H.K. Lee, H. Kanamori, P.C. Jennings, and C. Kisslinger (Ed.), International Handbook of Earthquake and Engineering Seismology, Part A, Ch. 41, 665–690, Academic Press.
Villaseñor, A. and E.R. Engdahl, 2007. Systematic relocation of early instrumental seismicity: Earthquakes in the International Seismological Summary for 1960-1963, Bull. Seism. Soc. Am.,97, 1820-1832.