Anomalous seismicity preceding the 1999 Izmit event, NW Turkey

SUMMARY The 1999 Izmit earthquake (1999 August 17, Mw= 7.4) was one of the largest earthquakes to occur in northwestern Turkey during the past 100 yr. This earthquake occurred along the Izmit–Sapanca fault within the Northern Anatolian Fault Zone. Variations in the generalized fractal dimensions (Dq) of clustering in time and space, the Gutenberg–Richter b-value, and earthquake frequency (N) are evaluated in detail over an 8.5 yr time period preceding the Izmit event. Spatial and temporal comparisons of the variations in these parameters reveal anomalous intermediate term behaviour over shorter timescales than previously observed. Significant correlation is observed between changes in b-value with the spatial and temporal fractal dimension of epicentre distribution. These correlations oscillate back and forth over 2–3 yr time intervals and suggest occurrence of significant instability in the nature of intermediate-term deformation along the fault zone. Seismotectonic behaviour immediately preceding the Izmit event is represented by a significant rise in b-value to a maximum of 2.26 accompanied by relatively small increases in D. The rapid rise of b is associated with an increased frequency of low magnitude seismicity. Although D (spatial and temporal) increase slightly in the 2–3 yr period preceding rupture, they remain less than 1 indicating that seismicity remains clustered prior to rupture. In areas where earthquake frequency or station density do not permit resolution of short-term variations of fractal scaling parameters within a few months of main rupture, an accelerated period of low-magnitude seismicity (high b-value) concentrated along a fault zone (D < 1) may suggest heightened probability of a forthcoming large event.

[1]  S. Vinciguerra.  Damage mechanics preceding the September October 1989 flank eruption at Mount Etna volcano inferred by seismic scaling exponents , 2002 .

[2]  P. Grassberger,et al.  Measuring the Strangeness of Strange Attractors , 1983 .

[3]  Steven N. Ward.  A multidisciplinary approach to seismic hazard in southern California , 1994 .

[4]  I. Main,et al.  A simple fracture‐mechanical model for the evolution of seismicity , 1992 .

[5]  Bruce E. Shaw,et al.  Generalized Omori law for aftershocks and foreshocks from a simple dynamics , 1993 .

[6]  Y. Kagan,et al.  Long‐term probabilistic forecasting of earthquakes , 1994 .

[7]  B. Gutenberg,et al.  Seismicity of the Earth and associated phenomena , 1950, MAUSAM.

[8]  Bruce E. Shaw,et al.  Patterns of seismic activity preceding large earthquakes , 1992 .

[9]  Warwick D. Smith.  The b-value as an earthquake precursor , 1981, Nature.

[10]  Thomas H. Wilson,et al.  Correlation of seismotectonic variables and GPS strain measurements in western Turkey , 2004 .

[11]  Alain Geiger,et al.  GPS‐derived strain rate field within the boundary zones of the Eurasian, African, and Arabian Plates , 2000 .

[12]  V. P. Dimri,et al.  Multifractal Approach to the Time Series of M≥7.0 Earthquake in Himalayan Region and its Vicinity during 1895-1995 , 2001 .

[13]  R. Olsson.  An estimation of the maximum b-value in the Gutenberg-Richter relation , 1999 .

[14]  Michael G. Norman,et al.  A fracture-mechanical cellular automaton model of seismicity , 1994 .

[15]  L. R. Sykes,et al.  Evolving Towards a Critical Point: A Review of Accelerating Seismic Moment/Energy Release Prior to Large and Great Earthquakes , 1999 .

[16]  Jean-Luc Chatelain,et al.  A fractal approach to the clustering of earthquakes: Applications to the seismicity of the New Hebrides , 1987 .

[17]  Stefan Wiemer,et al.  A Software Package to Analyze Seismicity: ZMAP , 2001 .

[18]  Ian G. Main,et al.  Statistical physics, seismogenesis, and seismic hazard , 1996 .

[19]  A. Hasegawa,et al.  Aftershock Activity of the 1999 İzmit, Turkey, Earthquake Revealed from Microearthquake Observations , 2002 .

[20]  I. Main,et al.  Classification of earthquake precursors from a fracture mechanics model , 1989 .

[21]  T. Hashimoto,et al.  Temporal variation of multifractal properties of seismicity in the region affected by the mainshock of the October 6, 2000 Western Tottori Prefecture, Japan, earthquake (M = 7.3) , 2002 .

[22]  K. Aki.  17. Maximum Likelihood Estimate of b in the Formula logN=a-bM and its Confidence Limits , 1965 .

[23]  S. Crampin,et al.  The MARNET radiolinked seismometer network spanning the Marmara Sea and the seismicity of Western Turkey , 1985 .

[24]  S. Crampin,et al.  Tectonics of the Marmara Sea region of Turkey: new evidence from micro-earthquake fault plane solutions , 1985 .

[25]  Ian G. Main,et al.  Temporal variations of the fractal properties of seismicity in the western part of the north Anatolian fault zone: possible artifacts due to improvements in station coverage , 1995 .

[26]  I. Main,et al.  Temporal variations in the fractal properties of seismicity in the North Anatolian Fault Zone between 31°E and 41°E , 1996 .

[27]  T. V. McEvilly.  Seismicity of the earth and associated phenomena , 1967 .

[28]  Florent Lyard,et al.  On the statistical stability of the M2 barotropic and baroclinic tidal characteristics from along‐track TOPEX/Poseidon satellite altimetry analysis , 2004 .

[29]  Silvia Castellaro,et al.  Regression problems for magnitudes , 2006 .

[30]  Warwick D. Smith.  Evidence For Precursory Changes In the Frequency‐Magnitude B‐Value , 1986 .

[31]  O. Nishizawa,et al.  Quasi‐static fault growth and cracking in homogeneous brittle rock under triaxial compression using acoustic emission monitoring , 2000 .

[32]  P. Sammonds,et al.  The evolution of seismicity at Parkfield: observation, experiment and a fracture-mechanical interpretation , 1992 .

[33]  G. Fiedler.  Local b-values related to seismicity , 1974 .

[34]  N. N. Ambraseys,et al.  The Seismic Activity of the Marmara Sea Region over the Last 2000 Years , 2002 .

[35]  T. Wilson,et al.  Evaluation of earthquake potential along the Northern Anatolian Fault Zone in the Marmara Sea using comparisons of GPS strain and seismotectonic parameters , 2006 .

[36]  M. N. Toksöz,et al.  Space-time migration of earthquakes along the North Anatolian fault zone and seismic gaps , 1979 .

[37]  Cataldo Godano,et al.  Mdtifractal analysis of earthquake catalogues , 1995 .

[38]  G. Karakaisis.  Accelerating seismic crustal deformation before the Izmit (NW Turkey) large mainshock of 1999 August 17 and the evolution of its aftershock sequence , 2003 .

[39]  Gregory L. Baker,et al.  Chaotic Dynamics: An Introduction , 1990 .

[40]  Yan Y. Kagan,et al.  Long-term earthquake clustering , 1991 .

[41]  J. McCloskey,et al.  Heterogeneity and the earthquake magnitude‐frequency distribution , 1999 .

[42]  Joseph F Labuz,et al.  Damage mechanisms in stressed rock from acoustic emission , 1995 .

[43]  X. Lei,et al.  Fractal structure and characteristic scale in the distributions of earthquake epicentres, active faults and rivers in Japan , 1999 .

[44]  M. Wyss,et al.  Minimum Magnitude of Completeness in Earthquake Catalogs: Examples from Alaska, the Western United States, and Japan , 2000 .

[45]  Jochen Zschau,et al.  Correlating variations of b values and crustal deformations during the 1990s may have pinpointed the rupture initiation of the Mw=7.4 Izmit earthquake of 1999 August 17 , 2002 .

[46]  Philip G. Meredith,et al.  A reinterpretation of the precursory seismic b-value anomaly from fracture mechanics , 1989 .

[47]  T. Wilson,et al.  Space-Time Correlations of Seismotectonic Parameters: Examples from Japan and from Turkey Preceding the İzmit Earthquake , 2002 .

[48]  Max Wyss,et al.  The major asperities of the 1999 Mw = 7.4 Izmit earthquake defined by the microseismicity of the two decades before it , 2000 .