Teresa Susagna

Analysis of macroseismic and instrumental data for the study of the 19 November 1923 earthquake in the Aran Valley (Central Pyrenees)

The 19 November 1923 earthquake in the Aran Valley (Central Pyrenees), with observed maximum intensityImax = VIII (MSK), has been studied through the compiling and reviewing of macroseismic information and collecting and processing early seismograms. Analysis of macroseismic data gives a focal depth ofh = 5 km and an anelastic attenuation coefficientα ≤ 10−3 km−1. Analysis of early instrumental records allows the computation of estimate of magnitude (ML = 5.6) and seismic moment (Mo = 1.1 × 1017 N × m) which are consistent with the values ofIo andh obtained from macroseismic data.

The European-Mediterranean Distributed Accelerometric Data-Base

We created an archive for European acceleration data, based on distributed database of accelerogram waveforms, accessed through the new European Earthquake Data Portal (http://www.seismicportal.eu). Data are open to the scientific and engineering community. Currently the 6 core partners contribute data from 1,379 earthquakes with magnitudes ranging from M1.0 to M7.4. Strong Motion Data are available with epicentral distances up to 1,000 km. Additionally, agencies are encouraged to contribute data. Waveforms included in the database are uniformly processed to create a set of engineering parameters that are used to search the database. In addition to the database, we compiled a survey of the existing accelerometric stations in the Euro-Med iterranean region. We expect this platform to be the basis for growing sharing of European Strong Motion Data in an open environment, in as near to real-time as is possible from network operators.

Recorded Ground Motion and Estimated Soil Amplification for the 11 May 2011 Lorca Earthquake

On 11 May 2011 an earthquake of magnitude 5.2 (M w ) hit the Murcia region of Spain causing significant damage to buildings in the town of Lorca. Accelerograms were recorded by stations of the Instituto Geográfico Nacional, and high-amplitude ground motions were observed at the Lorca station, with a peak ground acceleration (PGA) of 0.37 g. The contribution of a near-field component of ground motion is shown in time histories and in elastic response spectra. Features of near-field ground motions such as directivity could have significantly enhanced the ground shaking caused by this event. Local amplification effects in Lorca were investigated by the H/V spectral ratio technique and an array method. Information obtained from the geophysical field survey allowed the definition of representative soil columns and site classifications according to Eurocode 8. Modeling of site response is conducted for an example location. The aftershocks recorded at different sites confirm the soil amplification at these locations.

A European digital accelerometric database: statistical analysis of engineering parameters of small to moderate magnitude events

During the NERIES Project, an accelerometric database containing European digital information was developed. Besides event and station metadata, ground motion parameters, computed in a homogeneous manner, were assembled: PGA, PGV, AI, TD, CAV, HI and PSV(f,5%) (19,961 components, 2629 events, 547 stations). Merging small and moderate magnitude events produced a unique database capable of providing important information such as: (i) Correlations between several ground motion parameters follow analogous trends as in previous worldwide datasets, with slight corrections. (ii) Although PGA attenuations with distance show great uncertainties, four recent GMPEs recommended for Europe fit quite well the central 50% data interval for the distance range 10 < R < 200 km; outside these distances, they do not fit. (iii) Soil amplification ratios indicate that weak motion (low magnitudes and larger distances) shows larger amplification than strong motion (short distances and large magnitudes) as represented in UBC97 for the USA, but not in EC8 for Europe. (iv) Average spectral shapes are smaller than in the EC8. (v) Differences in amplification factors for PGA, PGV and HI for EC8 soil classes B and C, and differences in spectral shapes for these soil classes, indicate that EC8, Type 2 S-coefficient should be frequency dependent, as in UBC97.