Database of Individual Seismogenic Sources

The compilers of the DISS database guarantee the existence of all listed seismogenic sources, both Individual and Composite, and strive to describe them with the best possible accuracy. Nevertheless, they are well aware that the literature contains hypotheses and descriptions concerning a significantly larger number of potential seismogenic sources than those currently listed in the Database. In contrast with the aleatoric uncertainty normally associated with the inherent variability in the parameters of the expected earthquake rupture, the uncertainty related to the mere existence of a large fault is epistemic. This uncertainty may become crucial in deterministic seismic hazard analyses or even in a probabilistic approach dominated by large potential earthquake sources, yet it isn't easy to assess and may vary substantially depending on the region and different investigators. No matter how careful the work is, this type of uncertainty is generally not properly conveyed to the potential end-users of a seismogenic source database (e.g., Woo, 2005).

The compilers of DISS addressed this major source of uncertainty in seismic hazard analysis practice by identifying and describing several "Debated Seismogenic Sources." These are active faults that have been proposed in the literature as potential seismogenic sources, but their characterization was not considered reliable enough to be included in the other source categories of the Database. They may include:

• faults for which only minimal surface evidence is supplied in the literature;
• faults based on inherently ambiguous geological evidence;
• faults for which the literature offers highly contrasting views;
• faults that occur in low or very low seismicity areas;
• faults whose characteristics are in open contrast with nearby, better known and established seismogenic sources or violate documented tectonic and seismological evidence.

Similarly to the other categories of DISS sources, each Debated Seismogenic Source is identified by the code CCDS###, where:

• CC is the two-letter ISO 3166-1 code for names of officially recognized countries;
• DS identifies specifically the Debated Seismogenic Sources;
• ### is an ordinal between 1 and 999 (including leading zeroes).

The Debated Seismogenic Sources are represented in the Database as free-form polygons containing the potentially active structure with large margins. Instead of a more accurate symbol, we use this representation to overcome any possible ambiguity and error derived from the process of georeferencing the published maps of the active structures.

The reliability of DISS seismogenic sources is assessed by the database compilers, and hence it is their sole responsibility. The Database, however, was designed to allow quantification of all uncertainties involved in its compilation. Therefore, in addition to supplying formal uncertainty estimates for all sources that appear in the current release of the Database, the compilers wanted to share with the end-users why any given Debated Seismogenic Source was not considered reliable enough for consideration in other source categories of the Database. To this end, the compilers developed and compiled a questionnaire that helps focus the attributes of any seismogenic source, either proposed by the compilers themselves or discussed in the literature and assessing its reliability in a formalized step-by-step procedure. Each attribute was ranked as positive, negative or "not applicable," depending on whether that attribute increases or decreases the overall reliability of the potential seismogenic source or if it is undetermined. The questionnaires prepared for each Debated Seismogenic Source are supplied as support information to that source.

See the full version of the Questionnaire below.

References

Woo, G. (2005), Insurance Applications of Active Fault Maps Showing Epistemic Uncertainty, Eos Trans. AGU, 86(52), Fall Meet. Suppl., Abstract S23C-07.