Summary

In 1981 June and July two large earthquakes occurred on the Gowk Fault System in south-east Iran. Both earthquakes were associated with surface faulting showing a combination of reverse and right lateral strike-slip motion on parallel, adjacent faults striking north-south and dipping both east and west. Such motion can be seen to have occurred in the recent past and is responsible for the formation of elongated alluvium-filled depressions in the footwall region common to both the east- and west- dipping faults. The earthquake of June 11 involved motion along about 15 km of the Gowk Fault System with a moment of about 1.0 × 1026 dyne cm. The earthquake of July 28 was larger and occurred farther north with movement along at least 65km of the Gowk Fault System and a moment of about 7 × 1026 dyne cm. Surface faulting in both earthquakes was complex and spread over several kilometres width on en echelon fault segments as well as on faults dipping both east and west. The long-period WWSSN seismograms of these two mainshocks are unusually complicated and clearly made up of several individual subevents. Sensible interpretation of these waveforms without guidance from the surface faulting and the long-period SRO moment tensor inversion of Dziewonski & Woodhouse would be impossible. However, a combination of these three data sources allows a geologically plausible interpretation of the rupture processes in these earthquakes to be made.

Although the faulting in both mainshocks was on the same large-scale feature (the Gowk Fault), the rupture zones of the two earthquakes did not, apparently, overlap and were separated by a gap of 5 km along strike in which both coseismic and recent geological displacements are very small. Rupture in both mainshocks appears to have nucleated near this gap and to have propagated away from it. Other such gaps are visible along the irregular displacement of the northern fault break, and may have been the nucleation positions for individual subevents of the July 28 earthquake. Recognition of such nucleation sites is of obvious importance to earthquake prediction efforts.

References

Adeli
H.
,
1982
.
The Sirch (Kerman, Iran) earthquake of 28 Iuly 1981: a field investigation
,
Bull. seism. Soc. Am.
 ,
72
,
841
861
.
Ambraseys
N. N.
,
1978
.
The relocation of epicentres in Iran
,
Geophys. J. R. astr. Soc.
 ,
53
,
117
121
.
Ambraseys
N. N.
Arsovski
M.
Moinfar
A. A.
,
1979
.
The Gisk earthquake of 19 December 1977 and the seismicity of the Kuhbanan fault zone
 , UNESCO Puhl. No. FMR/SC/GEO/79/192, Paris,
47
PP.
Ambraseys
N. N.
Melville
C. P.
,
1982
.
A History of Persian Earthquakes
 .
Cambridge University Press
,
219
pp.
Asudeh
I.
,
1982
.
Pn velocities beneath Iran
,
Earth planet. Sci. Lett.
 ,
61
,
136
142
.
Asudeh
I.
,
1982
.
Seismic structure of Iran from surface and body wave data
,
Geophys. J. R. astr. Soc.
 ,
71
,
715
730
.
Bastani-Parizi
A.
,
1956
.
Malek and Jame Mozafari mosques
, in
Guide to the Kerman Monuments
 , pp.
49
58
,
Kerman Department of Education
, Kerman, Iran (in Farsi).
Bastani-Parizi
A.
,
1956
.
Mazar-e-Shah Nemat Olah Vali Kermani
, in
Guide to the Kerman Monuments
 , pp.
74
95
,
Kerman Department of Education
, Kerman, Iran (in Farsi).
Berberian
M.
,
1979
.
Earthquake faulting and bedding thrust associated with the Tabas-e-Golshan (Iran) earthquake of September 16, 1978
,
Bull. seism. Soc. Am.
 ,
69
,
1861
1887
.
Berberian
M.
,
1979
.
Evaluation of instrumental and relocated epicentres of Iranian earthquakes
,
Geophys. J. R. astr. Soc.
 ,
58
,
625
630
.
Berberian
M.
,
1981
.
Active faulting and tectonics of Iran
 , in
Zagros — Hindu Kush — Himalaya Geodynamic Evolution
 , eds
Delany
F. M.
Gupta
H. K.
, Geodyn. Series, Am. geophys. Un., pp.
33
69
.
Berberian
M.
Asudeh
I.
Arshadi
S.
,
1979
.
Surface rupture and mechanism of the Bob-Tangol (southeastern Iran) earthquake of 19 December 1977
,
Earth planet. Sci. Lett.
 ,
42
,
456
462
.
Brown
R. D.
Vedder
J. G.
Wallace
R. E.
Roth
E. R.
Yerkes
R. F.
Castle
R. O.
Waanen
A. O.
Page
R. W.
Eaton
J. P.
,
1967
.
The Parkfield-Cholame California, earthquakes of June- August 1966: surface geologic effects, water resource aspects and preliminary seismic data
,
Prof. Pap. U.S. geol. Surv.
 ,
579
,
66
pp.
Burdick
L. J.
Langston
C. A.
,
1977
.
Modelling crustal structure through the use of converted phases in teleseismic body waveforms
,
Bull. seism. Soc. Am.
 ,
67
,
677
691
.
Chen
W.-P.
Molnar
P.
,
1983
.
Focal depths of intracontinental and intraplate earthquakes and their implications for the thermal and mechanical properties of the lithosphere
,
J. geophys. Res.
 ,
88
,
4183
4214
.
Clark
M. M.
,
1972
.
Surface rupture along the Coyote Creek fault
 , in The Borrego Mountain earthquake of April 9, 1968, Prof. Pap. U.S. geol. Surv., 787,
55
86
.
Das
S.
Aki
K.
,
1977
.
Fault plane with barriers: a versatile earthquake model
,
J. geophys. Res.
 ,
82
,
5658
5670
.
Dimitrijevic
M. D.
,
1973
.
Geology of Kerman region, Rep. geol. Surv. Iran
 ,
Yu/52
,
334
pp.
Dziewonski
A. M.
Chou
T.-A.
Woodhouse
J. H.
,
1981
.
Determination of earthquake source parameters from waveform data for studies of global and regional seismicity
,
J. geophys. Res.
 ,
86
,
2825
2852
.
Dziewonski
A. M.
Woodhouse
J. H.
,
1983
.
An experiment in the systematic study of global seismicity: centroid-moment tensor solutions for 201 moderate and large earthquakes of 1981
,
J. geophys. Res.
 ,
88
,
3247
3271
.
Fitch
T. J.
,
1972
.
Plate convergence, transcurrent faults, and internal deformation adjacent to southeast Asia and the western Pacific
,
J. geophys. Res.
 ,
77
,
4432
4460
.
Hill
D.
Grabar
O.
,
1967
.
Islamic Architecture and its Decoration, A.D. 800–1500
 , 2nd edn, London.
Huckriede
R.
Kursten
M.
Venzlaff
H.
,
1962
.
Zur geologie des gebietes zwischen Kerman und Sagand (Iran)
,
Geol. Jb.
 ,
51
,
197
pp.
Jackson
J. A.
Fitch
T. J.
,
1979
.
Seismotectonic implications of relocated aftershock sequences in Iran and Turkey
,
Geophys. J. R. astr. Soc.
 ,
57
,
209
229
.
Jackson
J. A.
Fitch
T. J.
,
1981
.
Basement faulting and the focal depths of the larger earthquakes in the Zagros mountains (Iran)
,
Geophys. J. R. astr. Soc.
 ,
64
,
561
586
.
Jackson
J. A.
Gagnepain
J.
Houseman
G.
King
G.
Papadimitriou
P.
Soufleris
C.
Virieux
J.
,
1982
.
Seismicity, normal faulting and the geomorphological development of the Gulf of Corinth (Greece): the Corinth earthquakes of February and March 1981
,
Earth planet. Sci. Lett.
 ,
57
,
377
397
.
Jackson
J. A.
McKenzie
D. P.
,
1984
.
Active tectonics of the Alpine-Himalayan Belt between western Turkey and Pakistan
,
Geophys. J. R. astr. Soc.
 ,
77
,
185
264
.
Kanamori
H.
Anderson
D. L.
,
1975
.
Theoretical basis of some empirical relations in seismology
,
Bull. seism. Soc. Am.
 ,
65
,
1973
1095
.
Kanamori
H.
Stewart
G. S.
,
1978
.
Seismological aspects of the Guatemala earthquake of February 4, 1976
,
J. geophys. Res.
 ,
83
,
3427
3434
.
King
G.
Vita-Finzi
C.
,
1981
.
Active folding in the Algerian earthquake of 10 October 1980
,
Nature
 ,
292
,
22
26
.
Langston
C. A.
Helmberger
D. V.
,
1975
.
A procedure for modelling shallow dislocation sources
,
Geophys. J. R. astr. Soc.
 ,
42
,
117
130
.
Lindh
G.
Boore
D. M.
,
1981
.
Control of rupture by fault geometry during the 1966 Parkfield earthquake
,
Bull. seism. Soc. Am.
 ,
71
,
95
116
.
Matheson
S. A.
,
1976
.
Persia: an archaeological guide
 ,
2nd edn
,
Faber
, London,
358
pp.
Moinfar
A. A.
Idgaadi
M. E.
,
1982
. Preliminary note on the Golbaf and Sirch earthquakes of June 11th and July 28th 1981, Ministry of Housing & Urban Development, Building and Housing Research Centre, Teheran, Publ. No. 42,
33
pp.
Nogol
M. A.
Ghorashi
M.
Kadjar
M. H.
Sabzehei
M.
,
1983
.
Geological-structural investigation of the 21 Krordad 1360 Golbaf earthquake
 , Int. Rep. geol. Surv. Iran (in Farsi).
Peseckis
L. L.
Burdick
L. J.
,
1982
.
Station site characteristics of WWSSN stations in India and southern Asia
,
Bull. seism. Soc. Am.
 ,
72
,
1207
1218
.
Pope
A. U.
,
1965
.
Persian Architecture
 ,
Thames & Hudson
, London,
288
pp.
Sarfaraz
A.
Babakzadeh
J.
,
1965
.
Kerman investigation in the year 1344
 , unpublished Report,
Iranian Centre for Archaeological Research
,
six volumes
, Teheran.
Scholz
C. H.
,
1977
.
Transform Fault systems of California and New Zealand: similarities in their tectonic and seismic styles
,
J. geol. Soc. London
 ,
133
,
215
229
.
Soufleris
C.
Jackson
J. A.
King
G.
Spencer
C.
Scholz
C.
,
1982
.
The 1978 earthquake sequence near Thessaloniki (northern Greece)
,
Geophys. J. R. astr. Soc.
 ,
68
,
429
458
.
Tapponnier
P.
Molnar
P.
,
1979
.
Active faulting and Cenozoic tectonics of the Tien Shan, Mongolia and Baykal regions
,
J. geophys. Res.
 ,
84
,
3425
3459
.
Tchalenko
J. S.
Ambraseys
N. N.
,
1970
.
Structural analysis of the Dasht-e-Bayaz (Iran) earthquake fracture
,
Bull. geol. Soc. Am.
 ,
81
,
41
60
.
Tchalenko
J. S.
Berberian
M.
,
1975
.
Dasht-e-Bayaz, Iran: earthquake and earlier related structures in bed rock
,
Bull. geol. Soc. Am.
 ,
86
,
703
709
.
Valeh
N.
,
1973
. Geological map of Gowk, 1:100,000, Geological Survey of Iran.
Vaziri-Kermani
A. A.
,
1974
.
History of Kerman (Salarieh)
 , ed.
Bastani-Parizi
A.
,
Ebn-e-Sina
, Teheran, Iran (in Farsi).
Yielding
G.
Jackson
J. A.
King
G.
Sinvhal
H.
Vita-Finzi
C.
Wood
R. M.
,
1981
.
Relations between surface deformation, fault geometry, seismicity, and rupture characteristics during the El Asnam (Algeria) earthquake of 10 October 1980
,
Earth planet. Sci. Lett.
 ,
56
,
287
304
.