From Historical Seismology to Seismogenic Source Models to Seismic Risk: 20 Years On, Results and Challenges

Date: 4/26/2019

Time: 08:30 AM

Room: Pike

Over the past two decades Historical Seismology has experienced a silent revolution that turned it from purely descriptive to fully quantitative, transformed its outcomes from vaguely subjective to solidly reproducible, and – unbeknown to many – increased its relevance far beyond the mere computation of “activity rates” in the SHA practice.

In Italy this revolution was largely spawned by the inception of the Catalogue of Strong Earthquakes in Italy, or CFTI (see Ferrari et al. in this session): a large databases providing for each earthquake all felt intensities along with the precise identification of the reported sites and a description of the earthquake effects. CFTI allowed automatic processing of intensity data to derive the epicentral parameters, an equivalent magnitude and the geometric parameters of the prospective causative fault through a Fortran code termed Boxer (Gasperini et al., BSSA, 1999).

The improved data manageability and resolution allowed large Italian earthquake sequences to be investigated in depth, often revealing an unexpected source complexity and setting new constraints on the location and magnitude of the most significant shocks. This evidence contributed to unraveling the arrangement and behavior of large seismogenic fault systems, greatly supporting seismotectonic interpretations in areas dominated by tectonic complexity and blind faulting. Historical data have been used for calculating earthquake budgets to be compared with geodetically-determined tectonic strains, which allowed crucial investigations on the variability of seismic coupling and on earthquake recurrence models devised for seismic hazard assessment. Finally, the availability of the seismic history of all Italian municipalities served as a basis for a first-cut estimation of their vulnerability, thus contributing to the definition of priorities for seismic risk mitigation countrywide.

Little or none of all this would have been possible without Historical Seismology data, an often overlooked treasure that still awaits to be exploited in many seismogenic areas worldwide.

Presenting Author: Gianluca Valensise

Authors