A global catalogue of earthquake environmental effects

The primary goal of the 2008-2011 activities of the Focus Area will be the compilation of a global catalogue of earthquake environmental effects.
Similarly to traditional seismic catalogues, which commonly record intensity assessments based on damage to buildings, this global catalogue will be a compilation of characteristics of environmental effects caused by earthquakes in selected regions worldwide, collected in a standard method. Specific attention will be given to the more diagnostic features for the evaluation of ESI epicentral and local intensities. The web interface of the catalogue will be also improved in order to provide a more user-friendly upload and consultation of the information.
A successful catalogue requires a strong contribute by Regional Working Groups in providing data on earthquake environmental effects. If you want to collaborate to this project, do not hesitate to contact the Scientific Secretary.

Background and Rationale

Recent progresses in the field of paleoseismology have clearly shown that effects on natural environment are more strictly related to the earthquake magnitude (e.g. Wells & Coppersmith, 1994) than effects on humans and manmade structures. As revealed by the application of the ESI 2007 to case studies, intensity evaluations based on the characteristics and size of earthquake environmental effects provide a more reliable image of the earthquake in the epicentral area of strong to large seismic events (intensity ranging from IX to XII in the 12 degree scales). EEE allow a more accurate intensity evaluation for the highest degrees, when other scales are afflicted by saturation. Thus the ESI 2007 scale proved to be an invaluable tool for the assessment of seismic hazards.
The importance of the EEE’s in seismic hazard assessment had been clearly illustrated by the recent Chuetsu-Oki earthquake on 16th July 2007 (Mw = 6.6) that damaged the Kashiwazaki – Kariwa Nuclear Power Plant (KK NPP) in Central Japan. (the largest civilian nuclear facility in the world). This event was generated by a reportedly “blind” active structure located very close to the NPP site. In fact, damage to the NPP site was essentially due to ground failure and liquefaction. Moreover, this event produced a large number of environmental effects (liquefactions, landslides, ground cracks, coseismic uplift) in the surroundings of the KK NPP. Siting investigations performed in the 1980’s on the basis of Quaternary geology, historical and instrumental seismicity, geophysical prospecting, etc., had likewise excluded the presence of active faults in the proximity of the site (< 30 km), and judged the folds under the plant not active in the past 50,000 years. However, the occurrence of environmental effects was not considered in the earthquake scenarios resulting from NPP siting investigations.
This earthquake has dramatically shown that a traditional approach may be not adequate in terms of time window and resolution for a proper seismic hazard assessment. Therefore it needs to be integrated with a detailed characterization of coseismic effects produced on natural environment by “innovative” techniques, like paleoseismic investigations. To this end, a systematic revision, mapping and classification of contemporary and paleoseismic EEE data is necessary, with special focus on the most diagnostic features for the intensity assessment, such as surface faulting and liquefaction.
Pioneer inventories of earthquake environmental effects prepared in the frame of the 0418 INQUA project (2003-2007) are the EEE database and the catalogue of earthquake ground effects in Spain (Silva et al., 2007).

A preliminary proposal of structure for the catalogue

According to standard formats of seismic catalogues, one earthquake is described by one string of a table characterized by typical fields. Temporal and geographic references of the earthquakes are described by fields like “Date of occurrence” (Year, Month, Day, Hour, Min, Sec), “Epicentral Area”, “Epicentre Coordinates” (frequently Latitude, Longitude). The earthquake severity is shown by “Epicentral intensity” (I₀) and “Magnitude” (instrumental or estimated on the basis of macroseismic observations) fields. Of course, regional seismic catalogues may use different intensity scales as well as different magnitude definitions. Moreover, some additional fields for seismological parameters are frequently included, since they are customized on local characteristics of seismological data. This will reduce the level of earthquake comparability among different catalogues.
In order to guarantee the maximum comparability among earthquakes, the structure of a global catalogue has to follow the abovementioned typical standard formats. In the string below is reported a possible scheme:

The second part of the string should be more specifically focused on the characteristics of environmental effects. Surface faulting parameters (surface rupture length, maximum displacement, prevalent slip type) and the total area of secondary effects are necessary data for the assessment of I₀ through the ESI scale. A corresponding magnitude value (M_ESI) should be provided on the basis of empirical relationships between ESI intensity and magnitude “ad hoc” developed, similarly to those which relate magnitude and damage based-intensity evaluations. The example below shows a possible configuration of the string aimed at comparing the results of the ESI and traditional approaches, where the number of observations (N. eff., Np) provides a rough measure of the wealth of information behind the intensity evaluation. On equal terms of data input reliability, the final earthquake intensity degree will coincide with the maximum value.

The last field links the string to a report which summarizes the characteristics of environmental effects more in detail. This report should comprehend at least i) a descriptive introduction of the event; ii) a list of environmental effects classified by locality and corresponding local ESI intensity assessments; iii) a list of references. Additional issues could be ESI local intensity maps as well as photographs and sketches. Possible examples in this direction are illustrated in Silva et al. (2007) and Serva et al. (2007).

References

• Serva L., Esposito E., Guerrieri L., Porfido S., Vittori E. & Comerci V. (2007). Environmental Effects from some historical earthquakes in Southern Apennines (Italy) and macroseismic intensity asseessment. Contribution to INQUA EEE scale project. Quaternary International 173-174 (2007), 30-44.
• Silva P.G., Alfaro P., Azañón J.M. ,  Bardají T.,  Feriche M.  M.,  Giménez Carcía J.  J., Goy J.L. , Lario J. J., . Martínez-Díaz J.,   Reicherter K., Pérez-López R. ,  Rodríguez Pascua M.A.,   Zazo C.( 2008) -  AEQUA Catalogue of Earthquake Ground Effects in Spain: applications of the EEE INQUA Scale in the Iberian Peninsula (Preliminary report). Association Espanola para el Estudio del Cuaternario, 20 pp.