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SEISMOLOGICAL DATABASE FOR BANAT SEISMIC REGION (ROMANIA)–PART 2: THE CATALOGUE OF THE FOCAL MECHANISM SOLUTIONS

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A high quality Catalogue of Focal Mechanism Solutions of the earthquakes occurred in the Banat Seismic Region (Romania) (CFMSBSR) is presented. It comprises focal mechanism solutions (FMS) for 140 events, spanning 47 years (1959–2006). CFMSB includes three kinds of the FMS: i) collected FMS with their original parameters, ii) compiled FMS with modified parameters, iii) new FMS.
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Rom. Journ. Phys., Vol. 53, Nos. 78, P. 965–977, Bucharest, 2008
SEISMOLOGICAL DATABASE FOR BANAT SEISMIC REGION
(ROMANIA) – PART 2:
THE CATALOGUE OF THE FOCAL MECHANISM SOLUTIONS
E. OROS, M. POPA, E. POPESCU, I. A. MOLDOVAN
National Institute of Research and Development for Earth Physics, Bucharest, Romania;
eoros@mail.com, mihaela@infp.ro, epopescu@infp.ro, iren@infp.ro
Received June 28, 2007
A high quality Catalogue of Focal Mechanism Solutions of the earthquakes
occurred in the Banat Seismic Region (Romania) (CFMSBSR) is presented. It
comprises focal mechanism solutions (FMS) for 140 events, spanning 47 years
(1959–2006). CFMSB includes three kinds of the FMS: i) collected FMS with their
original parameters, ii) compiled FMS with modified parameters, iii) new FMS.
Key words: earthquakes, faults, focal mechanism solutions, Banat Seismic
Region.
1. INTRODUCTION
The earthquake source parameters provide critical information for global,
regional and local tectonic studies and seismic hazard analysis, as well as for
many types of seismological investigations. The knowledge of the stress field for
a given region, with a specific geological structure and tectonics, and the
understanding of the seismotectonic processes, which generate strong
earthquakes, are essential clues to define and characterize the seismogenic
sources.
The systematic studies of the focal mechanism solutions (FMS) in a large
geo-informational context, furnish fundamental data about some of the main
factors that control the seismic phenomenon, e.g. stress field peculiarities and the
types of faulting, the geometry of the faults and their spatial position against
maximum horizontal stress. These studies request particular Seismological
Databases that have to include a Catalogue of Focal Mechanism Solutions
(CFMS) for the earthquakes occurred within the territory of interest.
The main purpose of this paper is to present the complete and revised
CFMS for the earthquakes occurred in the western and south-western part of
Romania, known as Banat Seismic Region (BSR). This catalogue is one of the
main informational components of the Seismological Database elaborated for
BSR by [11]. CFMSB has also an important data field, not included in the
966 E. Oros, M. Popa, E. Popescu, I. A. Moldovan 2
present paper, namely Digital Tectonic and Geologic Map [10], a tool for
realistic use of CFMSB.
We used all available data about FMS from literature as well as new
information gathered from seismograms and seismic bulletins (e.g. polarities,
amplitudes and travel times for P and S waves). High quality hypocentral para-
meters and moment magnitude, M
w
, have been computed for all earthquakes cata-
logued. The parameters of the most FMS have been reconsidered on a new data
basis. New solutions were determined for the earthquakes occurred after 2004.
The catalogue contains FMS determined for 140 seismic events with
2.8 M
w
5.6, which occurred in BSR between 1959 and 2006. It is accessible
both in electronic and hard print formats. We consider CFMSB as being an
important contribution to improve and to update the existing seismological
databases, especially the seismotectonic one, elaborated for Romania and for the
Carpatho-Pannonian Basin.
CFMSB has a particular significance for the local seismic hazard
assessment in BSR because it brings new and valuable information useful for
knowing better the state of the stress in the crust and lithosphere and to highlight
the mutual relationship between the specific tectonics of the region and the
known patterns of seismicity revealed by [7–9, 12, 13].
2. DATA, ANALYSIS AND RESULTS
The information used to compile CFMSB presented in this paper come
from different sources, among which the most important are the following:
i) focal mechanism solutions collected from literature (published papers,
manuscripts and research reports, earthquake catalogues and bulletins); ii) travel
times and polarities of the first P waves gathered from the seismic bulletins and
the catalogues of the international seismological agencies, seismic stations
or/and seismological observatories; iii) travel times and polarities of the first P
waves picked from original seismograms obtained into the framework of the
international project EuroSeismos (www.storing.ingv.it/es_web); iv) travel times
and polarities of the first P waves from digital seismograms recorded by the
Romanian National Seismic Network after the ’80s and by the Banat Local
Seismic Network between 1995 and 2004 (http//:www.infp.ro); v) travel times
and polarities of the first P waves recorded by mobile stations; vi) amplitude of P
and S (SV, SH) waves.
A detailed analysis of the new sets of information and data was conducted
and the final processing of the inputs followed the next steps:
1. All events with FMS collected from the literature, the new ones
identified in this study using new data and those occurred since 2004 were
3 Focal mechanism solutions for Banat Seismic Region 967
(re)located using the Seisan Software package [4]. The moment magnitude, M
w
is adopted in the paper according to the Romanian Earthquake Catalogue,
Romplus [6]. M
w
has been directly computed from digital seismograms when
these ones were available or it has been obtained by conversion of the original
reported magnitudes M
i
to M
w
(Mi was M
L
, M
D
, M
S
or mb). We applied the
scheme for conversions defined by [6].
The seismic stations used in the study are shown in Fig. 1. The picture
emphasizes the good coverage of the stations used in our study vs. the position of
the epicenters from BSR. The short distances between epicenters and some of
the seismic stations assured better constraints to estimate the focal depths and the
parameters of FMS. The catalogue drafted in this phase covers the time interval
27.05.1959–28.06.2006 and comprises 167 events with solutions of focal
mechanisms that occurred in BSR and its neighborhoods.
Fig. 1 – The map of seismic stations which recorded at least one earthquake listed in the
CFMSB. Only the nearest stations to Banat Seismic Region (BSR) are displayed. The large
triangle with dotted limits encloses BSR. Small open triangles symbolize the seismic stations.
2. Focal mechanisms calculated for all earthquakes that occurred only
within the limits of the BSR drawn by [8], have been carefully selected for
location accuracy, with special attention on the station coverage and the number
of the polarities. A final catalogue with 140 FMS resulted. The map of epicenters
for these events is displayed in Fig. 2. In Fig. 3 the frequency distributions for
magnitudes and focal depths are displayed. As it can be seen in Fig. 3, the most
968 E. Oros, M. Popa, E. Popescu, I. A. Moldovan 4
catalogued events have magnitudes M
w
4.3 (92%) and cluster within three
focal depth intervals.
Table 1
Basic statistics of hypocenters quality locations for the earthquakes listed in Table 2
errors Mean Median Mode Minimum Maximum Std.Dev.
longitude E 3.4 3.6 2.5 1.4 14.3 2.12
latitude N 2.3 2.5 1.8 1.1 12.1 1.83
depth 3.4 3.6 2.8 1.4 12 2.03
errors/h ratio 0.29 0.32 0.29 0.11 2.15 0.30
Fig. 2 – Map of epicenters for the earthquakes listed in Table 1. BA, DA means Banat
and Danube Seismogenic Zones, respectively.
The high quality of the hypocentral parameters is pointed out by the errors
statistics synthesized in Table 1 and by the two main distributions presented in
Fig. 4, the latitude/longitude errors and the quality classes, defined by [6],
respectively. Most of the location errors are smaller than 5.0 km (75.1 % on
longitude and 88.3% on latitude).
5 Focal mechanism solutions for Banat Seismic Region 969
Fig. 3 – Frequency distributions of the a) magnitude (Mw) and b) focal depth for the events
listed in CFMSB (Table 2).
The earthquakes with FMS mapped in Fig. 2 are grouped into two main
seismo-active tectonic setting defined by several studies as major seismogenic
zones [7–9, 12, 15]. Thus, in the North-West the Banat Seismogenic Zone (BA)
develops corresponding to a depression area (Western Plain of Romania) and in
the South-East the Danube Seismogenic Zone (DA) that overlaps on the area of
the Carpathians Mountains is known.
3. All 140 events were checked for parameters of FMS consistency with the
new locations, new data and sometimes additional constraints (e.g. additional
polarities, amplitude of P and S waves on three components and ratio of SV/P,
SH/P, SH/SV amplitudes). Subsequently the FMS were recomputed with the
FocMec software [4, 17] using the new information: only P polarities (90%) or P
polarities and amplitude ratios (10%). More FMS have been (re)analyzed using
only the data from seismograms recorded at local distances, sometimes nearer
970 E. Oros, M. Popa, E. Popescu, I. A. Moldovan 6
Fig. 4 – Error limits and quality classes of the new hypocenters parameters: a) the distribution of the
errors of geographical coordinates of epicenters, b) the frequency of the quality classes of location
(A, B and C quality classes have been defined by [6]; A refers to the best quality), c) the distribution
of focal depth errors (km) vs. focal depth (km), d) the distribution of the focal depth errors/focal
depth ratio vs. focal depth.
than 1.5 times the focal depth, what means solutions well constrained [20]. We
determined new FMS for the earthquakes occurred after 2004, too. The main
parameters of the final FMS are listed in the simplified version of CFMSB
presented in Table 2.
In the Fig. 5 is displayed the distribution of the main types of faulting as
they are revealed by the statistics of the main parameters of FMS. The solutions
were sorted into faulting types based on strike, dip, and rake orientation
following the convention of Aki and Richards [1980]. Because these categories
are based on the fault slip angle, we determined the most probable fault plane in
order to determine the proper rake. For each focal mechanism, the fault plane
was chosen as the nodal plane that most closely matched the orientation of faults
in the vicinity, compiled and digitized by [10]. In most cases, the faulting type
was the same regardless of which nodal plane was assumed to be the fault plane.
7 Focal mechanism solutions for Banat Seismic Region 971
Table 2
Focal mechanism solutions for Banat Seismic Region of Romania. The parameters of focal mechanism
solutions are given in the two nodal plane (azimuth, dip and rake for Plane 1 and Plane 2) and P an T
axis (azimuth and plunge) following the convention by [1]. Explanation of catalogue entries: Date/d, m,
y-the date of earthquake/day, month and year; Ho/h, m-the origin time of earthquakes/hour and
minutes; lat and long-the geographical coordinates of the epicenters; h-focal depth; Mw-moment
magnitude; Plane 1 and Plane 2/Az, Di, Sl-nodal planes, strike, dip and rake; P and T/Az, Pl-P and T
axes/azimuth measured counter wise from North and their plunge; Po-number of polarities used to
determine the focal mechanism solutions; Ref-references sources used for collected and compiled data
No Date Ho lat long h M
w
Plane 1 Plane 2 P T Po Ref
d m y h m AzDi Sl AzDi Sl AzPlAzPl
1 27 5 1959 20 38 45.64 21.09 9 5.0 229 49 –153 121 70 –44 76 45 180 13 19 [8]
2 17 4 1974 1 31 46.03 21.04 16 4.9 271 61 172 5 83 29 135 15 232 25 18 [8]
3 22 6 1978 2 33 46.75 21.16 15 4.9 164 78 137 265 48 16 221 19 115 38 23 [3*]
4 22 6 1978 2 57 46.77 21.12 17 3.0 151 52 148 262 65 43 24 8 122 47 11 [3*]
5 21 10 1985 18 33 45.19 22.56 5 3.1 15 83 –156 282 66 –8 241 22 146 12 8 [3
#
]
6 22 4 1988 1 23 45.50 20.96 5 3.8 81 66 33 336 60 152 207 4 300 40 9 [8]
7 12 5 1988 7 8 45.46 23.05 19 3.6 95 60 –145 346 60 –35 311 45 221 0 10 [8]
8 29 11 1988 1 23 45.70 21.55 10 3.9 343 85 –38 77 52 –174 293 30 36 22 21 [13]
9 10 3 1989 16 24 45.35 23.11 7 3.5 33 59 –13 130 79 –148 356 30 258 13 7 [7
#
]
10 15 2 1990 10 18 45.57 22.82 19 3.3 87 80 38 349 53 167 213 18 315 33 6 [14
#
]
11 17 4 1990 4 35 44.92 22.88 19 3.4 133 60 52 10 47 137 249 7 350 57 14 [8,16]
12 12 7 1991 10 42 45.38 21.10 11 5.6 9 89 –168 279 78 –1 235 9 143 8 [20]
13 12 7 1991 16 29 45.42 21.12 11 4.3 100 59 –133 341 51 –41 315 54 219 5 27 [8,10]
14 12 7 1991 20 42 45.35 21.21 6 3.9 180 81 158 274 68 10 227 9 137 23 9 [8]
15 13 7 1991 4 33 45.40 21.17 14 3.8 4 72 4 273 86 162 320 10 227 15 13 [8]
16 13 7 1991 5 10 45.39 21.09 9 3.8 273 86 65 174 25 170 24 36 159 44 7 [8]
17 13 7 1991 14 6 45.42 21.13 10 4.1 310 56 –12 47 80 –145 274 31 174 16 10 [8]
18 13 7 1991 17 27 45.42 21.17 19 4.2 274 46 –27 23 71 –133 249 46 143 15 29 [8,10]
19 13 7 1991 17 56 45.38 21.22 13 3.9 41 53 –137 282 57 –46 249 54 342 2 20 [8,10]
20 13 7 1991 19 3 45.41 21.21 9 4.1 274 77 121 25 33 25 341 26 217 49 13 [8]
21 14 7 1991 17 3 45.41 21.15 9 4.1 192 52 –121 56 48 –57 38 66 303 2 16 [8,10]
22 14 7 1991 23 59 45.45 21.33 18 4.0 190 52 –135 69 56 –48 37 56 130 3 26 [8,10,16]
23 15 7 1991 15 45 45.38 21.12 12 4.2 24 51 –16 124 78 –140 352 36 249 17 11 [8]
24 18 7 1991 11 56 44.87 22.37 15 5.6 75 52 –124 303 49 –54 282 64 189 2 [20]
25 18 7 1991 12 3 44.77 22.29 13 3.6 35 76 –153 298 64 –16 259 29 165 8 15 [8]
26 18 7 1991 14 3 44.69 22.31 9 3.8 32 61 –129 271 47 –41 250 56 149 8 10 [8]
27 18 7 1991 21 51 44.99 22.47 17 3.3 203 80 –145 106 56 –12 70 31 330 16 9 [8]
28 19 7 1991 1 19 45.32 21.15 7 4.2 48 81 –143 311 54 –11 276 32 174 18 36 [8]
(continues)
972 E. Oros, M. Popa, E. Popescu, I. A. Moldovan 8
Table 2 (continued)
No Date Ho lat long h M
w
Plane 1 Plane 2 P T Po Ref
d m y h m AzDi Sl AzDi Sl AzPlAzPl
29 19 7 1991 1 27 45.31 21.17 10 5.1 199 77 –163 105 73 –14 63 21 332 3 53 [3*]
30 19 7 1991 2 23 45.33 21.08 6 3.7 36 49 –132 270 56 –52 238 59 334 4 9 [8]
31 19 7 1991 2 43 45.33 21.23 4 3.9 221 51 –63 2 46 –119 195 69 292 3 10 [8]
32 19 7 1991 5 24 45.28 21.11 8 3.8 31 65 –148 286 61 –29 250 40 158 3 13 [8,10]
33 19 7 1991 8 6 45.41 21.20 6 3.8 281 81 –49 21 42 –167 228 39 340 25 9 [8]
34 19 7 1991 15 42 45.08 22.26 13 3.5 258 82 –23 351 67 –171 212 22 306 10 10 [8]
35 19 7 1991 16 19 44.99 22.39 8 3.5 355 46 10 258 83 136 315 24 206 35 9 [8]
36 20 7 1991 3 36 45.30 21.12 9 4.2 40 44 61 258 53 115 330 5 228 69 22 [8,10]
37 20 7 1991 3 58 45.34 21.14 8 4.2 189 75 –140 87 52 –19 55 38 313 15 21 [8,10]
38 22 7 1991 15 45 45.40 21.15 15 3.8 17 75 –160 282 71 –16 240 24 149 3 8 [8]
39 29 7 1991 20 46 44.82 22.44 14 3.7 69 48 –38 187 63 –131 47 53 305 9 7 [8]
40 31 7 1991 11 22 45.31 21.12 7 3.9 17 51 56 244 50 125 130 1 221 64 19 [8,10]
41 1 8 1991 12 57 45.41 21.13 12 3.9 201 74 145 302 57 19 255 11 157 36 7 [8]
42 2 8 1991 0 51 45.27 21.18 12 4.1 199 60 –37 310 59 –144 164 46 255 1 23 [8]
43 6 8 1991 15 4 45.40 21.12 7 4.1 188 80 –15 281 75 –170 144 18 235 3 19 [8,10]
44 7 8 1991 19 24 45.29 21.15 12 4.0 191 71 –17 287 74 –160 150 25 59 2 26 [8,10]
45 12 8 1991 4 59 45.41 21.14 9 4.4 208 86 –21 300 69 –176 162 18 256 12 38 [8,10]
46 14 8 1991 23 36 45.45 21.30 12 4.5 111 65 –141 2 55 –31 331 45 234 6 26 [8,10,16]
47 15 8 1991 1 34 45.42 21.27 6 4.1 259 57 –163 160 76 –34 115 34 213 12 15 [8,10]
48 15 8 1991 19 35 45.42 21.28 11 4.1 289 60 –40 42 56 –143 254 49 346 2 10 [8]
49 4 9 1991 18 13 44.89 22.39 13 3.6 219 61 –73 7 33 –118 164 69 297 15 9 [8]
50 7 9 1991 7 28 45.45 21.22 16 3.7 293 75 –48 39 44 –158 244 44 353 19 10 [8]
51 9 9 1991 20 48 44.97 22.33 5 3.7 291 62 –47 48 50 –142 253 52 352 7 9 [8]
52 11 9 1991 22 10 45.33 21.04 13 3.6 202 80 127 305 38 16 264 26 147 43 9 [8]
53 13 9 1991 7 8 44.93 22.32 11 3.7 235 75 –45 340 47 –159 187 42 294 17 9 [8]
54 13 9 1991 12 12 45.44 21.16 10 3.5 277 71 –23 15 68 –159 235 30 326 2 9 [8]
55 15 9 1991 0 11 44.97 22.37 4 3.5 96 48 –121 318 50 –60 295 68 27 1 11 [8]
56 15 9 1991 18 26 44.91 22.39 13 3.9 20 40 –34 137 69 –125 5 53 252 17 14 [8]
57 17 9 1991 3 2 44.61 22.35 12 4.1 172 52 –168 75 81 –39 26 33 129 19 35 [8,10,16]
58 19 9 1991 20 40 45.00 22.19 20 3.5 48 67 –132 295 47 –32 271 49 167 12 7 [8]
59 25 9 1991 11 30 45.25 21.13 11 3.7 186 66 147 291 60 28 240 4 147 40 7 [8]
60 8 10 1991 8 51 45.46 21.23 9 4.1 307 61 28 203 66 148 256 3 163 39 14 [8]
61 14 10 1991 20 56 45.43 21.25 9 4.0 267 54 –37 21 61 –138 237 49 143 4 10 [8]
62 17 10 1991 14 37 45.43 21.16 5 3.9 274 75 –47 20 45 –158 225 43 334 18 10 [8]
63 24 10 1991 16 38 45.36 21.19 9 3.8 16 46 –9 112 84 –136 344 34 236 25 9 [8]
(continues)
9 Focal mechanism solutions for Banat Seismic Region 973
Table 2 (continued)
No Date Ho lat long h M
w
Plane 1 Plane 2 P T Po Ref
d m y h m AzDi Sl AzDi Sl AzPlAzPl
64 1 11 1991 12 29 45.19 22.95 20 3.8 247 54 –48 10 53 –133 218 57 309 1 14 [8,16]
65 21 11 1991 2 16 45.51 21.30 18 4.3 329 52 –51 96 52 –129 303 60 213 0 30 [8]
66 26 11 1991 19 15 45.45 21.29 18 3.8 317 47 111 108 47 69 213 0 303 75 8 [8]
67 2 12 1991 8 49 45.45 21.21 9 5.5 103 72 –13 194 86 –162 60 16 327 9 [20]
68 2 12 1991 10 52 45.49 21.25 13 4.0 322 54 –36 75 62 –138 292 48 197 5 9 [8]
69 12 12 1991 12 2 45.45 21.25 9 3.8 113 36 –30 228 73 –122 101 51 342 21 11 [8,10]
70 17 12 1991 6 22 45.40 21.12 11 3.5 14 48 –37 131 63 –131 351 52 249 9 11 [8,10]
71 18 12 1991 10 24 45.80 21.53 16 4.0 278 75 –31 17 60 –163 234 32 330 10 16 [7,10]
72 19 12 1991 3 12 45.94 21.62 19 4.1 148 65 –164 51 76 –26 7 28 101 7 55 [7,10]
73 21 12 1991 11 43 45.88 21.59 14 3.9 294 48 –30 45 68 –134 269 47 165 12 16 [8,10]
74 24 12 1991 11 11 45.44 21.17 6 4.0 47 61 172 141 83 29 271 15 8 25 15 [8,10]
75 26 12 1991 3 13 45.46 21.29 15 3.6 299 61 –5 31 86 –151 259 23 161 17 9 [8]
76 17 2 1992 11 0 44.83 22.37 14 3.6 47 41 –139 284 65 –57 239 57 350 14 12 [8,16]
77 2 3 1992 20 33 45.89 21.49 12 4.0 270 76 24 174 67 165 41 6 134 27 43 [7,10]
78 24 5 1992 15 46 45.84 21.67 4 3.8 63 61 138 177 54 37 121 4 27 49 9 [8]
79 11 6 1992 11 20 44.94 22.40 19 3.6 188 77 121 299 33 25 255 26 131 49 8 [8]
80 19 12 1992 9 34 45.56 20.95 9 4.2 289 62 41 177 55 145 52 4 146 48 47 [8,10]
81 23 12 1992 21 5 45.52 20.96 7 4.3 283 45 82 114 46 98 199 1 103 84 28 [8,10]
82 11 1 1993 0 49 45.90 21.20 15 3.8 82 75 –130 334 42 –23 312 45 201 20 11 [8]
83 14 1 1993 8 23 45.58 21.08 7 4.1 130 46 29 19 70 132 80 14 334 47 23 [8,10]
84 13 10 1994 13 49 45.54 21.31 16 4.1 51 68 –11 145 80 –158 10 23 276 8 20 [8,10,16]
85 13 10 1994 23 31 45.48 21.27 11 4.1 295 59 62 161 41 128 45 10 155 64 11 [8,16]
86 15 10 1994 1 42 45.47 21.12 19 4.3 63 61 42 309 54 143 185 4 279 49 35 [8,10,16]
87 12 11 1994 19 34 45.51 21.20 16 4.2 29 57 –161 288 74 –35 244 36 342 11 19 [8,10,16]
88 3 2 1995 0 55 45.56 21.28 16 3.5 38 58 –162 298 75 –33 254 34 351 11 12 [8]
89 12 2 1995 6 5 45.44 21.17 13 4.1 74 55 155 179 70 38 303 9 42 40 8 [8,16]
90 24 8 1995 15 14 45.41 21.15 10 4.1 23 80 29 288 61 169 152 13 249 28 20 [8,10,16]
91 20 12 1995 14 59 45.08 23.02 4 3.0 85 88 –168 355 78 –2 311 10 219 7 14 [8]
92 6 3 1996 10 50 46.28 23.55 8 3.7 275 71 –47 24 46 –153 229 46 335 15 9 [8]
93 24 3 1996 9 13 45.43 21.18 13 3.5 23 48 54 250 53 123 317 3 222 64 24 [8,10,16]
94 10 2 1997 8 38 45.37 23.71 10 3.1 84 82 158 177 68 9 132 10 39 21 8 [8]
95 17 6 1997 13 33 46.55 20.77 8 3.7 245 54 20 143 74 142 198 13 98 38 10 [19]
96 16 1 1998 5 13 45.06 23.32 4 3.5 245 64 131 2 47 37 307 10 204 52 21 [7,10]
97 22 4 1998 13 35 46.08 20.19 7 3.1 280 81 –120 175 31 –17 160 46 34 30 8 [8]
98 29 7 1998 15 31 45.38 23.15 13 3.3 88 83 60 346 31 166 203 31 328 44 16 [7]
(continues)
974 E. Oros, M. Popa, E. Popescu, I. A. Moldovan 10
Table 2 (continued)
No Date Ho lat long h M
w
Plane 1 Plane 2 P T Po Ref
d m y h m AzDi Sl AzDi Sl AzPlAzPl
99 30 7 1998 4 54 45.45 23.24 5 3.2 80 87 –41 173 49 –176 28 30 134 25 21 [7,10]
100 26 9 1998 11 15 44.95 23.81 8 3.0 124 62 53 1 45 138 239 9 343 56 11 [8]
101 29 9 1998 22 34 45.77 21.80 19 3.3 277 81 –42 15 49 –168 227 35 333 21 17 [7]
102 21 1 1999 18 44 45.58 21.34 14 3.5 240 59 15 142 77 148 194 12 97 32 8 [8]
103 3 9 1999 9 38 46.53 21.15 17 3.8 118 75 –160 23 71 –16 341 24 250 3 13 [7,10]
104 3 10 1999 4 43 45.84 21.04 13 3.2 254 61 –107 106 33 –62 129 69 356 15 20 [7,10]
105 8 10 1999 17 26 45.29 21.11 9 3.1 267 89 –24 357 66 –180 219 17 315 16 18 [7,10]
106 9 10 1999 1 1 45.39 21.05 9 3.1 194 66 –59 318 38 –139 146 57 262 16 15 [7,10]
107 9 10 1999 20 49 45.31 21.11 12 3.8 232 46 –125 97 54 –59 66 65 166 4 15 [7,10]
108 20 12 1999 23 40 44.50 21.76 13 4.4 28 44 –110 235 49 –72 212 76 312 3 28 [7]
109 21 12 1999 3 22 45.08 23.13 5 3.7 254 42 –144 136 67 –54 90 53 200 14 28 [7,10]
110 18 7 2000 13 54 44.54 22.42 15 3.3 25 63 –149 280 63 –31 243 40 153 0 14 [7,10]
111 22 7 2000 7 23 45.73 21.42 11 3.6 226 40 17 123 79 129 184 24 70 42 22 [7,10]
112 22 7 2000 7 51 45.74 21.44 12 3.3 256 41 –41 19 65 –123 244 57 133 14 13 [7]
113 16 8 2000 22 13 45.47 21.30 17 3.5 159 53 –30 268 66 –139 129 45 31 8 27 [8]
114 21 8 2000 10 28 45.72 21.40 7 3.4 260 68 –117 134 34 –41 133 58 10 19 8 [7]
115 5 10 2000 23 4 45.74 21.39 12 4.0 48 53 124 180 49 54 115 2 20 63 23 [7,10]
116 30 10 2000 16 53 45.75 21.39 10 3.6 58 54 120 194 46 56 127 4 28 66 15 [7,10]
117 3 1 2001 8 8 44.88 22.27 10 3.4 195 86 –15 286 75 –176 150 13 241 8 14 [7,10]
118 15 6 2001 8 4 45.25 23.04 5 3.5 214 46 16 113 79 135 171 21 63 39 14 [7,10]
119 20 6 2001 15 44 45.73 21.43 7 3.5 226 50 –134 102 57 –51 69 58 165 4 14 [7,10]
120 24 6 2001 0 52 45.35 21.13 11 3.4 21 84 8 290 82 174 155 1 246 10 8 [7]
121 2 8 2001 21 50 45.48 21.12 7 4.0 152 77 –57 262 35 –156 97 48 217 25 23 [8,10]
122 20 8 2001 19 44 45.75 21.40 8 3.3 65 75 149 164 60 17 117 10 21 32 10 [7]
123 6 4 2002 14 5 45.30 21.09 10 3.6 53 59 –46 171 52 –139 18 53 113 4 11 [7]
124 3 5 2002 13 10 44.73 21.62 7 3.6 27 66 –59 151 38 –139 339 57 95 16 8 [8]
125 17 5 2002 8 10 45.34 23.01 15 3.5 271 87 137 4 47 4 326 26 218 31 11 [8]
126 23 5 2002 3 26 44.73 21.66 8 3.4 180 47 –73 336 46 –107 168 78 258 1 26 [7,9,10]
127 24 5 2002 20 42 44.72 21.64 9 4.6 191 53 –148 80 65 –42 40 47 138 7 66 [7,9,10]
128 2 8 2002 9 31 44.76 21.64 20 3.4 3 79 –136 263 47 –15 233 38 126 20 6 [8]
129 2 8 2002 9 37 44.74 21.63 7 4.2 161 71 –36 264 56 –157 118 39 215 10 48 [7,9,10]
130 4 8 2002 18 27 44.85 21.67 18 3.5 156 70 55 40 40 148 271 17 25 52 9 [8]
131 19 6 2003 18 2 44.93 22.42 19 3.7 30 66 0 120 90 156 252 17 348 17 19 [8]
132 2 9 2004 16 40 45.51 20.53 16 3.4 288 54 –143 174 61 –42 138 49 232 4 11 [new]
133 22 10 2004 5 37 44.92 22.25 15 4.0 239 46 –126 105 54 –59 74 65 173 4 22 [new]
(continues)
11 Focal mechanism solutions for Banat Seismic Region 975
Table 2 (continued)
No Date Ho lat long h M
w
Plane 1 Plane 2 P T Po Ref
d m y h m AzDi Sl AzDi Sl AzPlAzPl
134 14 2 2005 23 37 45.42 22.51 20 3.7 98 56 –53 225 49 –131 66 60 163 4 11 [new]
135 20 3 2005 9 51 45.12 22.73 8 3.6 202 57 –14 300 78 –146 166 32 67 14 13 [new]
136 17 7 2005 7 30 45.52 21.32 6 2.8 250 51 16 150 78 140 205 17 102 36 11 [new]
137 17 7 2005 7 39 45.51 21.30 6 2.8 255 51 146 8 64 44 129 8 228 49 11 [new]
138 10 12 2005 7 56 44.53 22.27 19 3.5 179 75 20 84 71 164 311 3 42 24 8 [new]
139 5 2 2006 10 52 44.70 21.69 12 3.3 164 52 –117 24 45 –60 12 69 273 4 12 [new]
140 28 6 2006 17 24 44.58 21.77 8 2.9 19 64 –124 256 42 –41 243 57 133 12 7 [new]
n.b.– *from [18]; # from [16]; [new] are the FMS computed in this study.
Fig. 5 – The distribution of the main types of faulting in Banat Seismic Region (1959–
2006): l-ss, left-lateral strike-slip; o-n l-ss, oblique-normal left-lateral strike-slip; n,
normal; o-n r-ss, oblique-normal right-lateral strike-slip, r-ss, right-lateral strike-slip; o-r
r-ss, oblique-reverse right-lateral strike-slip; r, reverse; o-r l-ss, oblique-reverse left-
lateral strike-slip.
For a total of 50 events the faulting is oblique normal, for 6 – normal, for 37 –
strike slip, for 45 – oblique reverse, and for 2 – reverse. This great variety of
faulting types may be explained by the fact that in the catalogue there are many
earthquakes belonging to some complex seismic sequences (foreshocks and
aftershocks) and also many earthquakes with small magnitudes occurred in
different geological settings. It is known that generally these events are
controlled by stress-strain ratio after a strong earthquake and also by the local
stress conditions and geology.
3. CONCLUSION
The most recent and comprehensive Catalogue of Focal Mechanism
Solutions (CFMSB) for the Banat Seismic Region (BSR, the western and south–
western territory of Romania) has been achieved and presented in this paper.
976 E. Oros, M. Popa, E. Popescu, I. A. Moldovan 12
This catalogue, along with the Digital Tectonic and Geological Maps of Banat
Seismic Region, are main components of a high quality seismological database
elaborated at regional scale [11].
CFMSB is of great importance for the complex study of the entire
Carpatho–Pannonian Realm due to its content (140 Focal Mechanism Solutions)
and the high quality of the parameters of the location of hypocenters as well as
of the FMS parameters.
Acknowledgement. This research has been partially carried out in the framework of the
National Research and Development Programme, CERES/HASVER project, of the Minister for
Education and Research, Romania, under Contract no. 4–15/4.11.2004. The study of the historical
events has been possible by the partnership of the first author within the EuroSeismos Project and
by the useful colaboration of Dr. Graziano Ferrari and Dr. Marco Caciagli from SGA Bologna, Italy.
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We have found spatial variations in seismic stress indicators at the Yellowstone volcanic field, Wyoming, by examining source mechanisms of 25 years of network-recorded earthquakes, 1973-1998. Yellowstone seismicity is characterized by swarms of earthquakes (MC < 3) within the 0.64 Ma Yellowstone caldera and between the caldera and the eastern end of the 44-km-long rupture of the 1959 MS7.5 Hebgen Lake earthquake. We relocated more than 12,000 earthquake hypocenters using three-dimensional velocity models. Focal mechanisms calculated for 364 earthquakes, carefully selected for location accuracy, reveal predominantly normal faulting; however, fault orientations vary across the Yellowstone caldera. Specifically, focal mechanism T axes trend N-S in the vicinity of the Hebgen Lake earthquake fault zone NW of the Yellowstone caldera and rotate to ENE-WSW 35 km east of there. This rotation of the T axis trends occurs in the area of densest seismicity north of the caldera. Stress inversions performed using earthquake first-motion data reveal a similar pattern in the minimum principal stress orientations. The extension directions derived from the focal mechanisms and stress inversions are generally consistent with extension directions determined from geodetic measurements, extension inferred from alignments of volcanic vents within the caldera, and extension directions determined from regional normal faults. The N-S trending Gallatin normal fault north of the caldera is a notable exception; we find extension to be perpendicular to the direction of past extension on the Gallatin fault in the area immediately south of it. We interpret this N-S extension north of the caldera to be related to postseismic viscoelastic relaxation in the upper mantle and lower crust following the Hebgen Lake earthquake. The dominantly extensional tectonic regime at Yellowstone inferred from these results demonstrates the influence of NE-SW Basin and Range extension in this area.
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Extract In seismology, a wealth of data-processing programs are available, and a seismic observatory typically makes use of several. A common problem is the lack of a proper database structure which prevents effective use of the data, particularly with data from different sources. A primary goal of SeisAn is to organize data from all kinds of seismic stations into a simple database and to provide most of the tools needed for routine processing. The SeisAn database is a way of organizing data by using the directory and file structure, and is not a relational data system with general access techniques such as SQL, which usually is meant by the term “database.” In addition, the intention is to facilitate research tasks by integrating additional programs to work directly on the database. A second goal is that SeisAn must work in an identical manner under Sun (Solaris-1 and -2), Linux, and MS-Windows, and...
Catalogue of Earthquake Focal Mechanism Solutions for the Pannonian Region (42-52 N; 12-28 E)
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