TOWARDS A SEISMOGENIC SOURCSOURCEE MODEL OF THE DINARIDES KASTELIC VANJA1, TIBERTI MARA MONICA1, ROVIDA ANDREA2, ALBINI PAOLA2, BASILI ROBERTO1 1- INGV - Roma1; 2 - INGV - Milano-Pavia e-mail: [email protected] Outline Geology-based seismogenic source models are becoming the fundamental input for seismic hazard assessment at the scale of an entire country. In this work, we illustrate in simple steps the complex process that leads from basic data to a fully-fledged seismogenic source model of the Dinaride thrust belt, running along coastal Croatia, Montenegro and part of Albania. We started from a layer of basic geological and structural data and explored a wide range of indicators of recent tectonic activity, such as drainage anomalies/diversions and displaced or warped geological markers. We then analyzed the interplay of these indicators with known or prospective tectonic structures. To the picture thus obtained, we added a layer with a revised historical seismic catalog and selected a few earthquakes for which we re-estimate epicenter and magnitude. At the end of our analyses we combined all these data in a structured GIS database. With these data at hand, we also compared the longer-term indicators with present-day stress/strain data such as GPS velocities and earthquake focal solutions. Following the approach already developed for the construction of the Database of Individual Seismogenic Sources for Italy, we developed a seismogenic source model for the Dinarides in which the better constrained seismogenic faults have been mapped and parameterized and made ready for use in seismic hazard practice. 1. Regional structural and tectonic setting 2. Drainage anomalies and local geological characteristics a a Dubracina river -52 Ricina old river bed -56 -75 -67 -105 Ricina river -56 45 45 -57 -55 Suha Ricina river -57 -55 -50 -55 -58 -66 -65 -50 -57 -60 -45 V. Paklenica river -48 -56 -58 -52 M. Paklenica river -63 -64 -60 abandoned river bed -60 Krupa river notch depth (Benac etal, 2004) Zrmanja river notch depth (Benac etal., 2008) 44 44 abandoned river bed Krka river Cikola river Prokljansko jezero b Cetina river abandoned river bed abandoned river bed Active channel AbandonedAbandoned Active channel Tara river channels Neretva river Hutovo blato channels 43 43 Trebišnjica river Trebišnjica river ProgressiveProgressive Boka Kotorska shift of the Dubrovacka river shift of the Moraca river streamstream channel channel duedue to to anticline anticline 0 0 50 Grdovica river 50 100 100 growthgrowth y river Vjenica river kilometers kilometers x river b 42 42 Bojana river 4 km 13 20 13 14 15 16 17 18 19 20 14 15 16 17 18 19 Figure 1: Regional geologic setting and traces of active faults for the costal and off-shore parts of the Dinaride structure (data on geological Figure 2: Map of courses of rivers in the costal parts of the Dinarides with spotted drainage anomalies. Upper right figure shows depth formations taken from onegeology internet portal). position of submerged marine notch in the Kvarner area (data taken from Benac etal., 2004; Benac etal., 2008). The lower right figure demonstrates hydrographic conditions of Bojana river with a set of abandoned and active river channel. 3. Historical seismicity 4. Focal mechanism solutions and orientation of mean SH stress axis a 1870 1802 1750 1838 1776 a 1925 1904 RijekaRijeka 6.5 1750 VinodolVinodol 1909 1721 1916 5.5 7.5 1972 1939 1323 45 45 Rijeka 5.5 SenjSenj Rijeka VinodolVinodol 1648 Mali Lošinj 5.5 1930 1699 1390 SenjSenj 1178 1387 SenjSenj 1717 1399 epicenter location 1343 44 intensity value at a given location 44 1614 1407 1399 1418 ZadarZadar 1667 Trogir SplitSplit b 1496 1480 Metkovic b Metkovic 43 43 1544 1473 1482 8.5 1481 1667 1479 1496 4.5 9.5 1472 1608 9 9.5 DubrovnikDubrovnik 10 DubrovnikDubrovnik 1482 1631 Dubrovnik 8.5 1667 8.5 1520 9 KotorKotor 10 0 50 Kotor 0 50 100 1639 100 1608 10 kilometers 1563 kilometers 10 1632 1444 42 42 UlcinjUlcinj 7 1699 epicenter location 8 intensity value at a given location Ulcinj 13 14 15 16 17 18 19 20 13 14 15 16 17 18 19 20 Figure 3: Historical earthquakes along the costal and off-shore parts of the Dinarides. The figures on the right show two selected historical Figure 4: Map of focal mechanism solutions for earthquakes in the Dinaride region (from Pondrelli etal., 2006 together with orientation of earthquakes with reported intensity values; the 1750 Rijeka in the upper figure and 1667 Dubrovnik earthquake in the lower figure. mean SH stress axis obtained from various data sets (taken from Heidbach etal., 2008). 5. GPS vectors 6. Source model P E B A K A A K C U J V O I I R S L K IV E A U V T D A U I L Z Strike O P 45 North 45 W i d t Rake h Y R A K Top Dip depth th No +) ng rth st ( A Le (+ Ea D T ) A R ) Z - E st ( Sou B We th Bottom (-) S depth A S R V C A I 44 L A V Depth (+) K R 44 A S M E P J A IR Z K TIJA S R P A Geometry L V 1 I H S I V Location: Lat, Lon, Depth Size: Length, Width T E V S Orientation: Strike, Dip T S A 43 L K 43 R B Behavior D I L I A N L Rake A P Slip Rate Earthquake Magnitude 0 50 0 100 50 100 O K kilometers kilometers H S 42 42 13 14 15 16 17 18 19 20 13 14 15 16 17 18 19 20 Figure 5: GPS vectors obtained for the area of the Dinarides (data taken from Caporali etal., 2009). IDSource SourceName MinDepth MaxDepth StrikeMin StrikeMax DipMin DipMax RakeMin RakeMax SlipRateMin SlipRateMax MaxMag HRCS001 Mljet 2 15 280 330 30 45 70 110 0.12 0.5 6 References HRCS002 Hvar 3 15 260 310 40 65 20 70 0.1 0.45 6.1 Basili R., G. Valensise, P. Vannoli, P. Burrato, U. Fracassi, S. Mariano, M.M. Tiberti, E. Boschi (2008), The Database of Individual Seismogenic Sources (DISS), version 3: HRCS003 Imotski 2 20 290 320 50 70 95 130 0.1 0.4 6 summarizing 20 years of research on Italy's earthquake geology, Tectonophysics, doi:10.1016/j.tecto.2007.04.14 Benac, Č., M. Juračić and T. Bakran-Petricioli, Submerged tidal notches in the Rijeka Bay NE Adriatic Sea: indicators of relative sea-level change and of recent tectonic HRCS004 Eastern Mid-Adriatic offshore 2 12 270 310 35 60 70 100 0.15 0.45 5.5 movements, Marine Geology 212 (2004), pp. 21–33. HRCS005 Velebit 2 18 270 340 45 70 80 140 0.1 0.4 6 Benac, Č., M. Juračić and I. Blašković, Tidal notches in Vinodol Channel and Bakar Bay, NE Adriatic Sea: indicators of recent tectonics, Marine Geology 248 (2008), pp. 151–160. HRCS006 Vinodol - Rijeka 1 15 310 325 45 60 100 140 0.2 0.4 6 Caporali, A., et al., Surface kinematics in the Alpine–Carpathian–Dinaric and Balkan region inferred from a new multi-network GPS combination solution, Tectonophysics (2009), doi:10.1016/j.tecto.2009.04.035 MECS001 Montenegro offshore 1 15 290 330 25 45 60 100 0.15 0.8 7.2 DISS Working Group, 2009, Database of Individual Seismogenic Sources (DISS), Version 3.1: A Compilation of Potential Sources for Earthquakes Larger than M 5.5 in Italy and Surrounding Areas: http://diss.rm.ingv.it/diss/. OneGeology - Making Geological Map Data for the Earth Accessible: http://www.onegeology.org/. Figure 6: Composite seismogenic sources (see sketch to the right for definition) for the coastal and off-shore parts of the Dinarides. Table Heidbach, O., Tingay, M., Barth, A., Reinecker, J., Kurfeß, D. and Müller, B., The World Stress Map database release 2008 doi:10.1594/GFZ.WSM.Rel2008, 2008. shows the values of the parameters depicting each source (data taken from DISS 3.1, 2009). Pondrelli, S., Salimbeni, S., Ekstrom, G., Morelli, A., Gasperini, P., and Vannucci, G., 2006, The Italian CMT dataset from 1977 to the present: Physics of the Earth and Planetary Interiors, v. 159, p. 286–303, doi:10.1016/j.pepi.2006.07.008..