1062 Bulletin of the Seismological Society of America, 90, 4, pp. 1062–1081, August 2000 Ground-Motion Scaling in the Apennines (Italy) by Luca Malagnini, Robert B. Herrmann, and Massimo Di Bona Abstract Regressions over a data set of broadband seismograms are performed to quantify the attenuation of the ground motion in the Apennines (Italy), in the 0.25– 5.0 Hz frequency band. The data set used in this article consists of over 6000 hori- zontal-component seismograms from 446 events, with magnitude ranging from M w  2 to M w  6.0. Waveforms were collected during recent field experiments along the Apennines. Data from two MedNet broadband stations, located in central and southern Apennines, were also used. Seismograms are bandpass-filtered around a set of sampling frequencies, and the logarithms of their peak values are written as AMP( f, r)  EXC( f, r )  SITE( f )  D(r, r , f ). ref ref EXC(f , r ref ) is the excitation term for the ground motion at the hypocentral distance r ref . SITE(f ) represents the distortion of the seismic spectra induced by the shallow geology at the recording site. D(r, r ref , f ) includes the effects of the geometrical spreading, g(r), and of a frequency-dependent crustal attenuation Q. It is determined as a piecewise linear function, allowing to consider complex behavior of the regional attenuation. A first estimate of D(r, r ref , f ) is obtained using a coda normalization technique (Aki, 1980; Frankel et al., 1990) and used as a starting model in the inversion of the peak values. Then, by trial and error, the empirical D(r, r ref , f ) is fitted using a trilinear geometrical spreading, with crossover distances at 30 and 80 km, and the crustal parameter 0.10 f Q( f )  130 ; f  1.0 Hz ref  f ref These results suggest a low-Q crust in the entire Apennines in the 0.25–5.0 Hz range, implying that the seismic hazard in the region may be dominated by the local seis- micity. The final section is devoted to highlight the limitations of the formula proposed by Console et al. (1988) to estimate duration magnitudes M d in Italy. Introduction The assessment of seismic hazard is probably the most important contribution of seismology to society. The predic- tion of the earthquake ground motion has always been of primary interest for seismologists and structural engineers. A deterministic approach is done by matching shape and amplitude of every single pulse in the seismograms. This point of view is very important in seismology, since it allows us to obtain important information about the seismic source, and also a quantitative description of the medium through which the energy propagates. Although waveform modeling is widely and successfully used in global, long-period seis- mology, and even at regional distance, a different approach must be used to describe the high-frequency ground motion at short distances from the source because the complexity of the physical system (i.e., the rupturing fault coupled with a strongly heterogeneous Earth) goes beyond a critical level. In treating high-frequency strong ground motion recordings (accelerograms), we thus require a statistical approach. In- stead of trying to reproduce the details of the ground accel- eration in the time domain, we use a source model and a regional scaling law to predict its spectral shape and ampli- tudes at various source-receiver distances. Peak values in the