Dmitry A. Storchak

A New ISC Service: The Bibliography of Seismic Events

Online Material: Journals in the ISC Event Bibliography. The International Seismological Centre (ISC) is a not‐for‐profit organization with the primary mission of producing the definitive summary of the seismicity of the Earth (ISC Bulletin; ISC, 1964–2013). This is achieved thanks to a unique international cooperation in the seismological community that allows the ISC to collect, integrate, and finally process seismological bulletins (location parameters, station data, moment tensor solutions, felt reports, etc.) from approximately 130 agencies worldwide. Seismic (earthquakes or man‐made) events parameters and station data are publicly available via the ISC website (www.isc.ac.uk, last accessed January 2014). In 2012 we started to set up a new database to link parametric data related to seismic events (earthquakes or anthropogenic events) in the ISC Bulletin to publications considering specific seismic events. Such association is often needed by researchers in order to identify and gather information related to seismic events. Usually bibliographic searches (such as Google Scholar) are used by typing a text string containing a name for the seismic event or the region and date it occurred. Such a search may need to be repeated several times to account for all possible transliterations of a place name, several different ways of specifying a date and a variety of names of the area where the seismic event has occurred. For example, the great Sumatra earthquake of 2004 could be searched as “Sumatra‐Andaman,” “Banda‐Aceh,” “Aceh‐Sumatra,” etc. The results then have to be merged and the duplicates removed. The procedure is daunting and often leads to unsatisfactory results. The ISC Event Bibliography database allows users to search for publications linked to seismic events in the ISC Bulletin. This association enables users to perform searches based on event parameters (e.g., location and time of the event) and/or publications parameters (e.g., author name, journal, year of …

Discrepancies in earthquake location between ISC and other agencies

The different operating requirements of the International Seismological Centre (ISC) from those of the National Earthquake Information Service of the US Geological Survey(NEIS), and of the prototype International Data Center to monitor the Comprehensive Test Ban Treaty (pIDC), result in some discrepancies between earthquake locations computed by the three agencies. For larger events recorded by many stations the differences are small, but for some smaller events differences in location of up to 20° may occur. The largest discrepancies are found for small events in areas where later analysis by ISC has the benefit of additional readings from regional seismograph networks and where ISC has made a different interpretation of the station readingsavailable to pIDC and NEIS. We identify regions where such discrepancies occur most frequently, and give some examples for which the augmented data set of ISC has resulted in significant improvement for specific earthquakes. NEIS and, particularly, pIDC produce their results more speedily than ISC, and these form a valuable starting point for the later, more complete ISC analysis, which is commonly considered the most definitive compilation of global earthquake information.

Categorical Colormap Optimization with Visualization Case Studies

Mapping a set of categorical values to different colors is an elementary technique in data visualization. Users of visualization software routinely rely on the default colormaps provided by a system, or colormaps suggested by software such as ColorBrewer. In practice, users often have to select a set of colors in a semantically meaningful way (e.g., based on conventions, color metaphors, and logological associations), and consequently would like to ensure their perceptual differentiation is optimized. In this paper, we present an algorithmic approach for maximizing the perceptual distances among a set of given colors. We address two technical problems in optimization, i.e., (i) the phenomena of local maxima that halt the optimization too soon, and (ii) the arbitrary reassignment of colors that leads to the loss of the original semantic association. We paid particular attention to different types of constraints that users may wish to impose during the optimization process. To demonstrate the effectiveness of this work, we tested this technique in two case studies. To reach out to a wider range of users, we also developed a web application called Colourmap Hospital.

A scheme to set preferred magnitudes in the ISC Bulletin

One of the main purposes of the International Seismological Centre (ISC) is to collect, integrate and reprocess seismic bulletins provided by agencies around the world in order to produce the ISC Bulletin. This is regarded as the most comprehensive bulletin of the Earth’s seismicity, and its production is based on a unique cooperation in the seismological community that allows the ISC to complement the work of seismological agencies operating at global and/or local-regional scale. In addition, by using the seismic wave measurements provided by reporting agencies, the ISC computes, where possible, its own event locations and magnitudes such as short-period body wave mb and surface wave MS. Therefore, the ISC Bulletin contains the results of the reporting agencies as well as the ISC own solutions. Among the most used seismic event parameters listed in seismological bulletins, the event magnitude is of particular importance for characterizing a seismic event. The selection of a magnitude value (or multiple ones) for various research purposes or practical applications is not always a straightforward task for users of the ISC Bulletin and related products since a multitude of magnitude types is currently computed by seismological agencies (sometimes using different standards for the same magnitude type). Here, we describe a scheme that we intend to implement in routine ISC operations to mark the preferred magnitudes in order to help ISC users in the selection of events with magnitudes of their interest.