GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.1 35 Tab. 1 - Location of earthquakes with M 5.0 occurred the 18 January 2017.         Date Longitude Latitude Depth Mw 2017-01-18 09:25:41.06 13.290281 42.560377 8.30 5.1 2017-01-18 10:14:10.62 13.290887 42.550322 9.10 5.5 2017-01-18 10:25:24.43 13.292401 42.524957 9.14 5.4 2017-01-18 13:33:37.40 13.279016 42.484053 9.86 5.0 New Data. We present new earthquake locations computed by using the location tool NonLinLoc (NLL, Lomax et al. , 2000) and focal mechanisms obtained using first polarity techniques (Hypoellipse code; Lahr, 1999; FPFIT code; Reasenberg and Oppenheimer, 1985). The dataset comes from the careful manual analysis performed by the analysts of the Italian Seismic Bulletin. Epicentral and hypocentral distribution of the earthquakes recorded the week before and following the 18 January show a clear ‘jump’ of the seismicity from the north to the south, in the area of Capitignano with a deepening moving towards the south and the activation of a complex fault system. The area activated is contiguous to the distribution of the 2009 seismicity when a series of Mw > 5 events activated an almost flat segment, of the low-dip Campotosto fault confined between 6 and 9 km of depth (Valoroso et al. , 2013). For the focal mechanism, we collected 50 solutions with good quality factor and more than 20 P-wave polarities picked: 15 focal mechanisms for earthquakes occurred the January 18 th , and 35 related to the week before and after 18. The first motion data describe only the early part of the source which may or may not be representative of the whole source process for an earthquake: in this case, the solutions show strong complexity of the activated fault segments with sometimes substantial difference between parameters reported from TDMT and RCMT catalog (http://cnt.rm.ingv.it/tdmt , Scognamiglio et al. 2009; http://autorcmt.bo.ingv.it/quicks. html, Pondrelli et al. , 2011). References Boncio P., Lavecchia G., Pace B.; 2004. Defining a model of 3D seismogenic sources for seismic hazard assessment applications: the case of central Apennines (Italy). Journal of Seismology 8/3, 407-425. Lahr, J.C.; 1999, revised 2012: HYPOELLIPSE: a computer program for determining local earthquake hypocentral parameters, magnitude, and first-motion pattern U.S. Geological Survey Open-File Report 99–23, version 1.1, 119 p. and software, available at https://pubs.usgs.gov/of/1999/ofr-99-0023/. Lomax A., Virieux J., Volant P. and Berge C.; 2000:  Probabilistic earthquake location in 3D and layered models: Introduction of a Metropolis-Gibbs method and comparison with linear locations , in Advances in Seismic Event Location Thurber, C.H., and N. Rabinowitz (eds.), Kluwer, Amsterdam, 101-134. Pondrelli S., Salimbeni S., Morelli A., Ekström G., Postpischl L., Vannucci G. and Boschi E.; 2011: European- Mediterranean Regional Centroid Moment Tensor Catalog: solutions for 2005-2008 , Phys. Earth Planet. Int., 185(3), 74-81. Reasenberg P.A. and Oppenheimer D.; 1985: FPFIT, FPPLOT and FPPAGE: FORTRAN Computer Programs for Calculating and Displaying Earthquake Fault-Plane Solutions. US Geological Survey Open-File Report 85-739, 109 p. Rovida A., Locati M., Camassi R., Lolli B., Gasperini P. (eds); 2016: CPTI15, the 2015 version of the Parametric Catalogue of Italian Earthquakes , Istituto Nazionale di Geofisica e Vulcanologia. doi :http://doi.org/10.6092/ INGV.IT -CPTI15. Scognamiglio L., Tinti E., Michelini A .; 2009: Real-Time Determination of Seismic Moment Tensor for the Italian Region , Bulletin of the Seismological Society of America, 99(4):2223-2242, DOI: 10.1785/0120080104 Valoroso L., Chiaraluce L., Piccinini D., Di Stefano R., Schaff D., Waldhauser F., 2013: Radiography of a normal fault system by 64,000 high-precision earthquake locations: The 2009 L’Aquila (central Italy) case study . Journal of Geophysical Research: Solid Earth, 118(3), 1156-1176.