Shaking Maps Based on Cumulative Absolute Velocity and Arias Intensity: The Cases of the Two Strongest Earthquakes of the 2016–2017 Central Italy Seismic Sequence

Antonio Costanzo

doi:10.3390/ijgi7070244

Abstract

By referring to the two strongest earthquakes of the 2016–2017 Central Italy seismic sequence, this paper presents a procedure to make shaking maps through empirical relationships between macroseismic intensity and ground-motion parameters. Hundreds of waveforms were processed to obtain instrumental ground-motion features which could be correlated with the potential damage intensities. To take into account peak value, frequency, duration, and energy content, which all contribute to damage, cumulative absolute velocity and Arias intensity were used to quantify the features of the ground motion. Once these parameters had been calculated at the recording sites, they were interpolated through geostatistical techniques on the whole struck area. Finally, empirical relationships were used for mapping intensities, i.e., potential effects on the built environment. The results referred to both earthquake scenarios that were analyzed and were also used for assessing the influence of the spatial coverage of the instrumental network. In fact, after the first events, the Italian seismic network was subjected to the addition and thickening of sensors in the epicentral area, especially. The results obtained by models only dependent on ground-motion parameters or even on the epicentral distance were compared with the official ShakeMaps and the observed intensities for assessing their reliability. Finally, some suggestions are proposed to improve the procedure that could be used for rapidly assessing ground shaking and mapping damage potential producing useful information for non-expert audience.

Highlights

Observations about the effects of seismic shakings are at the base of macroseismic intensity scales, such as Rossi–Forel (RF, [1]), Mercalli–Cancani–Sieberg (MCS, Sieberg, [2]), Modified Mercalli (MM, [3,4]), Medvedev–Sponheuer–Kárník (MSK, [5]), and the European Macroseimic Scale (EMS, [6])
Details are provided about the two phases: (1) the interpolation of the engineering ground-motion parameters CAV and AI through geostatistical techniques and (2) the application of relationships between these parameters and macroseismic intensity
The author proposed a method to produce ground-motion shaking maps in terms of cumulative absolute velocity and Arias intensity and, these were converted into intensity maps through some relationships available in literature

Summary

Introduction

Observations about the effects of seismic shakings are at the base of macroseismic intensity scales, such as Rossi–Forel (RF, [1]), Mercalli–Cancani–Sieberg (MCS, Sieberg, [2]), Modified Mercalli (MM, [3,4]), Medvedev–Sponheuer–Kárník (MSK, [5]), and the European Macroseimic Scale (EMS, [6]). Today, instrumental seismology offers the possibility of correlating many observed data (macroseismic intensity) with parameters widely used for engineering purposes (ground-motion measures), making it possible to obtain empirical models for linking the two variables. In many areas of the world strongly exposed to seismic hazard, seismic networks can provide ground-motion recordings with dense spatial coverage, and these data are often available in a relatively short period of time. These data can be used to determine the location and magnitude of the earthquake, as well as ground-motion shaking maps by interpolation of ground-motion parameters, which are directly obtained by recordings. Intensities predicted on a regular grid can be useful to make inferences about the level of strong ground motion experienced after a larger earthquake in localities where little instrumental data are available [9]

Methods

Results

Conclusion