Seismological Research Letters Volume 80, Number 6 November/December 2009 967 doi: 10.1785/gssrl.80.6.967 INTRODUCTION his paper discusses the source- and site-efects on the distri- bution of macroseismic intensity, estimated or observed, fol- lowing the 29 July 2008 M 5.4 earthquake in the greater Los Angeles metropolitan region. We refer to the instrumental intensities according to the ShakeMap procedure (Wald et al. 2006) and the U.S. Geological Survey (USGS) Community Internet Intensity Map (CIIM; Atkinson and Wald 2007). he CIIMs are also known as the “Did You Feel It?” question- naires (DYFI). Both ShakeMap and CIIM are openly avail- able through the USGS Web site ( http://earthquake.usgs.gov/ eqcenter ). Note that the traditional modiied Mercalli intensi- ties (MMI; Wood and Neumann 1931) from the so called felt reports are not available for the study earthquake. hree original techniques designed to address intensi- ties are used here: 1) a simple kinematic formula for S-body- waves, KF (Sirovich 1996, 1997); 2) a “parametric KF scenario” (Sirovich and Pettenati 2004b, 2009; Pettenati and Sirovich 2006; Pettenati et al. 2008); and 3) the isoseismals obtained through natural neighbor interpolation (Sirovich et al. 2002; and see below. We also test our KF parametric technique for hazard plan- ning and its chance of improving fast information ater moder- ate earthquakes (mostly in regions with insuicient instrumen- tal coverage, where an isotropic, predictive, empirical equation is not satisfactory). Intensities are treated here as integer values for two rea- sons: irst, to adhere to the original deinition of MMI by Wood and Neumann (1931), and second, because our strategic target is the treatment of the remarkable database of high-quality tra- ditional macroseismic observations, obtained by seismologists and historians, which is available in Europe going back at least to the XVI–XVII centuries (see, for example, the Italian inten- sity data in Stucchi et al. 2007). THE AVAILABLE INTENSITIES Figure 1 shows the ShakeMap instrumental intensities near the meizoseismal area, modiied to indicate integer values rather than real numbers. For simplicity, we omitted the digital elevation model. he triangles represent the recording instru- ments used to rapidly calibrate the extent of shaking. hanks to the good instrumental coverage, the intensities were mostly derived from a rapid analysis of strong-motion recordings. he original data was provided by the USGS as gridded MMI values ( http://earthquake.usgs.gov/eqcenter/shakemap/sc/ shake/14383980/#download, 31 July 2008). Note the structure of the intensity ield in Figure 1. In particular, see a zone (arrow) of lower I in a westerly direc- tion from the epicenter. hen, the shape of the total area of I = V suggests ampliication and/or strong propagation/radia- tion toward Northridge (west-northwest), Mission Viejo and Murrieta (southeast; see Figure 1), and to the north-northeast and northeast (for the westernmost part of the San Fernando basin, see the second part of the Discussion). In the same igure, the previously mentioned indentation illed with I = V in the Downey-Rowland-Hacienda area is indicated approximately by an arrow. In the following igures, the arrows indicate the same position as in Figure 1, to facilitate comparisons. Figure 2 shows a close-up of the original USGS Community Internet Intensity Map (CIIM), with regions of I = VI as dark gray and I < VI as light gray. ( http://pasadena. wr.usgs.gov/shake/ca/STORE/X14383980/ciim_display.html; 22 August 2008; 40,733 responses). Intensities were, however, rounded to integers from the original real numbers; see the Web site for standard colors and details. Note the position of the epicenter (star) and the shape of the I = VI area. In par- ticular, we point out the 71 DYFI responses from the Rowland and Hacienda heights areas, because they are close to the epi- center and have intensities slightly less than V. However, there are many more zip codes of intensity V or less to the west of the epicenter; for example, the 69 DYFIs from Santa Fe Springs, 74 from Downey, 156 from La Habra, 50 from Norwalk, 56 from Miranda, and other data produce the large concavity of the I = VI area, similar to the indentation in Figure 1 (thick arrow used for comparison). We also note that outside of the principal area of I = VI, only two zip codes (Long Beach 90822 and Compton 90222) experienced intensities close to VI. he four remaining dark gray areas (rounded to VI) experienced Source- and Site-effects in the Intensities of the M 5.4 29 July 2008 Earthquake in South Los Angeles Livio Sirovich, Franco Pettenati, and Denis Sandron Livio Sirovich, Franco Pettenati, and Denis Sandron National Institute of Oceanography and Experimental Geophysics, Trieste, Italy