Earthquakes,Mud Volcano Eruptions,and Fracture Formation Hazards in the South Caspian Basin: Statistical Inferences from the Historical Record

Abstract

Based on data since 1832 from 533 earthquakes and 220 mud volcanoes in the Azerbaijan region, an analysis is given of: (a) the occurrence likelihood of weak, medium and strong earthquakes, the latter capable of causing significant damage; (b) the likely directions from which damaging earthquake waves can arrive; (c) the likelihood of a mud volcano hazard (ejected breccia and/or mud flows and/or flame ignition) in temporal association with an earthquake; and (d) the likelihood of fracture formation associated with mud volcanic eruptions.

The Chirag region of the South Caspian Basin is used to illustrate application of the methods because of the potential significance of the region for hydrocarbon exploration involving rigs susceptible to the above hazards.

The statistical information would indicate that the occurrence likelihood for a 7-balls or higher damaging earthquake in the Chirag region corresponds to an average waiting time of around 5,000 yrs; a medium strength (6-balls or higher) earthquake should occur, on average, in the region every 1,200 yrs, while a weak earthquake (5-balls or higher) is likely to occur, on average, every 110 years.

The most likely direction of longitudinal seismic waves from earthquakes of sufficient strength to cause significant damage in the Chirag region, be the earthquake epicenter in the region or at a remote focus, is roughly east and west, with a slight prevalence for a westward origin.

There is some correlation between earthquake actively and mud volcano activity, suggesting that mud volcanoes occur between zero to five years prior to earthquakes. But the correlation is not sharply delineated due to the paucity and quality of currently available data.

For surface fractures, associated with mud volcano eruptions, which can be meters wide and can stretch for a kilometer or more, only volcanoes with five or more eruptions were used to estimate the likelihood of fracture occurrence, yielding an average of about 30% chance of occurrence. The low number and low quality of data did not permit any more detailed investigation of fracture parameters – such as average width, length or offset.

In view of the potential hazards for oil rigs in the offshore South Caspian Basin, it would seem that organized, high quality, data collection both offshore and onshore should be rapidly undertaken as a vital adjunct to drilling operations in order to sharpen the assessments of risk factors presented here.

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References

Abikh

G.V.

, 1939, On the islands occurring in the Caspian Sea and information on the theory of mud volcanoes in the Caspian area, Trudy Instituta AzFAN, Vol. 12, (in Russian).

Agalarova

E.B.

, 1969, Characteristics of the orientation of stresses acting at the foci of earthquakes in the Apsheron Peninsula and Caspian Sea, Fizika Zemli, No. 7, (in Russian).

Agamirzoev

R.A.

, 1976, The seismic regionalization of the Azerbaijan SSR, In: Seismotectonics of some regions of the USSR, Moscow, Nauka, (in Russian).

Agamirzoev

R.A.

Gyul'

E.K.

, 1972, Seismotectonics of the Apsheron area and the Lower Kura Basin, Baku, Elm, (in Russian).

Agamirzoev

R.A.

Gyul'

E.K.

, 1973a, Regional Seismotectonics of the Caspian Sea, In: Seismogenic structures and seismic dislocations, Moscow, VNIIgeofizika, (in Russian).

Agamirzoev

R.A.

Gyul'

E.K.

, 1973b, The Kura and Caspian earthquakes, Izv. AN AzerbSSR, Ser. Nauk i Zemle, No. 2, (in Russian).

Agamirzoev

R.A.

Gyul'

E.K.

, 1983, Seismotectonics of the Caspian Sea and the characteristics of seismogenic zones, In: Geological and geomorphological studies of the Caspian Sea, Moscow, Nauka, (in Russian).

Bagirov

Nadirov

Lerche

, 1996, Flaming Eruptions and Ejections from Mud Volcanoes in Azerbaijan: Historical and Statistical Risk Assessment (this volume).

Kuliev

F.T.

, 1979, Equation for the macroseismic field of Azerbaijan. Seis. Bull, of the Caucasus, (in Russian).

10.

Malinovskii

N.V.

, 1938, Seisms accompanying mud eruptions Trudy AzFAN SSSR. Ser. fiziko-khimicheskaya, Vol. 3/38 (in Russian).

11.

Nadirov

Bagirov

Tagiyev

Lerche

, 1996, Flexural plate subsidence, sedimentation rates, and structural development of the super-deep South Caspian Basin Marine and Petroleum Geology (submitted August 1995).

12.

Panakhi

B.M.

, 1988, Seismotectonic territories of the Caspian Sea, Author's abstract for a Candidate's dissertation, Tbilisi, Georgia, (in Russian).

13.

Panakhi

B.M.

Kasparov

V.A.

, 1988, Problems of the seismic region in the Caspian Sea. Izv. AN. Azerbssr., Serie Nauk i Zemla, No. 1, (in Russian).

14.

Rakhmanov

R.R.

, 1987, Mud volcanoes and their value in the prediction of gas and oil at depth, Moscow, Nedra, (in Russian).

15.

Richter

C.F.

, 1958, Elementary seismology, W.H. Freeman & Co., San Francisco.

16.

Riznichenko

Yu V.

(Ed.) 1960, Methods for the detailed study of seismicity. Trudy IFZ AN SSSR. No. 9, (in Russian).

17.

Riznichenko

Yu V.

, 1985, Selected works, problems in seismology, Moscow, Nauka, (in Russian).

18.

Shebebalin

N.V.

, 1955, On the relationship between the energy and focal depth of earthquakes, Izv. An SSSR, Ser. Geofiz., No. 4, (in Russian).

19.

Shebebalin

N.V.

, 1968, Methods for using engineering and seismological data for establishing seismic regions, In: Seismic Regions of the USSR, Nauka, Moscow, (in Russian).