ALBERT

Description:    The Cheliff region has experienced some significant earthquakes in the last century (1937, 1954, and 1980). The most destructive one is that of El Asnam on October 10, 1980, Ms = 7.3 (Io = IX), which destroyed the Chlef city (formerly El Asnam) and its surrounding villages. On December 16, 2006 a moderate earthquake (Mw = 5.0) hit the Cheliff region. The maximum observed intensity (Io = V: MSK-scale) was observed at Abou El Hassen, Benaria, Bouzghaïa and Tadjena. No damages or human losses were recorded. Nevertheless, minor cracks on walls of the old school at Tadjena were observed. The point source focal mechanism of the event was determined by inverting the waveforms of three regional broadband stations of the ADSN (Algerian Digital Seismic Network). It corresponds to thrust-reverse faulting with a strike-slip component. The stress tensor obtained by the inversion of the 15 focal mechanisms available in the Cheliff region exhibits a well constrained compression axis σ1 horizontal and trending N145°. The NW dipping nodal plane indicating a NE–SW thrust fault with a right-lateral component (strike, dip, rake = 249, 38, 137) is more compatible with the regional stress tensor than the steep dipping NNE-SSW nodal plane showing reverse faulting with a left-lateral component (strike, dip, rake = 15, 65, 60). Accordingly, the Tadjena moderate size earthquake can be related to the Boukadir active fault bordering the lower Cheliff basin to the north, a situation similar to that of the El Asnam fault bordering the middle Cheliff basin to the north. Content Type Journal Article Pages 1-15 DOI 10.1007/s00024-011-0337-8 Authors H. Beldjoudi, Centre de Recherche en Astronomie Astrophysique et Géophysique, BP 63 route de l’observatoire, Bouzaréah, Alger, Algérie B. Delouis, Laboratoire Géoazur, Université de Nice-Sophia Antipolis, 250 rue Albert Einstein, Bâtiment 4, 06560 Valbonne, France A. Heddar, Centre de Recherche en Astronomie Astrophysique et Géophysique, BP 63 route de l’observatoire, Bouzaréah, Alger, Algérie O. B. Nouar, Centre de Recherche en Astronomie Astrophysique et Géophysique, BP 63 route de l’observatoire, Bouzaréah, Alger, Algérie A. Yelles-Chaouche, Centre de Recherche en Astronomie Astrophysique et Géophysique, BP 63 route de l’observatoire, Bouzaréah, Alger, Algérie Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553

Description:    A temporary earthquake station network of 11 seismological recorders was operated in the Bursa region, south of the Marmara Sea in the northwest of Turkey, which is located at the southern strand of the North Anatolian Fault Zone (NAFZ). We located 384 earthquakes out of a total of 582 recorded events that span the study area between 28.50–30.00°E longitudes and 39.75–40.75°N latitudes. The depth of most events was found to be less than 29 km, and the magnitude interval ranges were between 0.3 ≤ M L  ≤ 5.4, with RMS less than or equal to 0.2. Seismic activities were concentrated southeast of Uludag Mountain (UM), in the Kestel-Igdir area and along the Gemlik Fault (GF). In the study, we computed 10 focal mechanisms from temporary and permanents networks. The predominant feature of the computed focal mechanisms is the relatively widespread near horizontal northwest-southeast (NW–SE) T -axis orientation. These fault planes have been used to obtain the orientation and shape factor (R, magnitude stress ratio) of the principal stress tensors (σ 1 , σ 2 , σ 3 ). The resulting stress tensors reveal σ 1 closer to the vertical (oriented NE–SW) and σ 2 , σ 3 horizontal with R  = 0.5. These results confirm that Bursa and its vicinity could be defined by an extensional regime showing a primarily normal to oblique-slip motion character. It differs from what might be expected from the stress tensor inversion for the NAFZ. Different fault patterns related to structural heterogeneity from the north to the south in the study area caused a change in the stress regime from strike-slip to normal faulting. Content Type Journal Article Pages 1-17 DOI 10.1007/s00024-011-0347-6 Authors Elcin Gok, Earthquake Research and Implementation Center, Dokuz Eylul University, Izmir, 35160 Turkey Orhan Polat, Department of Geophysics, Engineering Faculty, Dokuz Eylul University, Izmir, 35160 Turkey Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553

Description:    Sea fog is typically formed and developed under a set of favorable environmental conditions, which are associated with the station pressure changes, sea level pressure, winds, temperature, water vapor supply, and sea surface temperature. Understanding of these environmental factors during the evolution of a sea fog episode is crucial for forecasting the occurrence and severity of sea fogs over the ocean and adjacent coastal areas. In this study, the large-scale environment variability of six fog events over the Yellow Sea was investigated. It was realized in the present study that the northwest Pacific Ocean high (NPH) is vital to fog formation over the Yellow Sea. In our study, six fog cases can be basically divided into two types: (1) pressure-weakening type, (2) pressure-strengthening type. The former type happened in spring and the latter type in summer. Prevailing southerly winds, accompanied with the well-positioned NPH, may supply a large amount of warm water vapor for the fog formation and maintenance. The intensity of the air temperature inversion is stronger in summer cases than that in spring ones. The wind direction change from south to north and the unstable lower atmosphere may lead to fog’s dissipation. This study may provide a comprehensive understanding of sea fog’s onset, maintenance, and dissipation over the Yellow Sea. Content Type Journal Article Pages 1-18 DOI 10.1007/s00024-011-0348-5 Authors Pengyuan Li, Laboratory of Physical Oceanography, Department of Marine Meteorology, Ocean University of China, No. 238, Songling Road, 266100 Qingdao, People’s Republic of China Gang Fu, Laboratory of Physical Oceanography, Department of Marine Meteorology, Ocean University of China, No. 238, Songling Road, 266100 Qingdao, People’s Republic of China Chungu Lu, NOAA/Earth System Research Laboratory, GSD5, 325 Broadway, Boulder, CO, USA Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553

Description:    A catalog for northeast India and the adjoining region for the period 1897–2009 with 4,497 earthquakes events is compiled for homogenization to moment magnitude M w,GCMT in the magnitude range 3–8.7. Relations for conversion of m b and M s magnitudes to M w,GCMT are derived using three different methods, namely, linear standard regression, inverted standard regression (ISR) and orthogonal standard regression (OSR), for different magnitude ranges based on events data for the catalog period 1976–2006. The OSR relations for M s to M w,GCMT conversion derived in this paper have significantly lower errors in regression parameters compared to the relations reported in other studies. Since the number of events with magnitude ≥7 for this region is scanty, we, therefore, considered whole India region to obtain the regression relationships between M w,GCMT and M s,ISC . A relationship between M w,GCMT and M w,NEIC is also obtained based on 17 events for the range 5.2 ≤ magnitude ≤ 6.6. A unified homogeneous catalog prepared using the conversion relations derived in this paper can serve as a reference catalog for seismic hazard assessment studies in northeast India and the adjoining region. Content Type Journal Article Pages 1-7 DOI 10.1007/s00024-011-0339-6 Authors Ranjit Das, Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee, India H. R. Wason, Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee, India M. L. Sharma, Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee, India Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553

Description:    While it is obvious that large-scale gravity studies should account for the sphericity of the Earth, each case should be examined. If a geometry model is very large for the 3D-gravity calculation, it cannot be correctly defined in Cartesian coordinates. Because of the Earth’s curvature it is necessary to use spherical coordinates, the importance of which is shown in this paper. The calculation of the gravity for a cylinder reveals, 1 m above the center of the cylinder, a relative difference of 13% between the models with Cartesian and spherical coordinates. Content Type Journal Article Pages 1-8 DOI 10.1007/s00024-011-0353-8 Authors Hasan Çavşak, Geophysics Engineering Department, Karadeniz Technical University, 61080 Trabzon, Turkey Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553

Description:    Anomalously low values of friction observed in layers of submicron particles deformed in simple shear at high slip velocities are explained as the consequence of a one nanometer thick layer of water adsorbed on the particles. The observed transition from normal friction with an apparent coefficient near μ  = 0.6 at low slip speeds to a coefficient near μ  = 0.3 at higher slip speeds is attributed to competition between the time required to extrude the water layer from between neighboring particles in a force chain and the average lifetime of the chain. At low slip speeds the time required for extrusion is less than the average lifetime of a chain so the particles make contact and lock. As slip speed increases, the average lifetime of a chain decreases until it is less than the extrusion time and the particles in a force chain never come into direct contact. If the adsorbed water layer enables the otherwise rough particles to rotate, the coefficient of friction will drop to μ  = 0.3, appropriate for rotating spheres. At the highest slip speeds particle temperatures rise above 100°C, the water layer vaporizes, the particles contact and lock, and the coefficient of friction rises to μ  = 0.6. The observed onset of weakening at slip speeds near 0.001 m/s is consistent with the measured viscosity of a 1 nm thick layer of adsorbed water, with a minimum particle radius of approximately 20 nm, and with reasonable assumptions about the distribution of force chains guided by experimental observation. The reduction of friction and the range of velocities over which it occurs decrease with increasing normal stress, as predicted by the model. Moreover, the analysis predicts that this high-speed weakening mechanism should operate only for particles with radii smaller than approximately 1 μm. For larger particles the slip speed required for weakening is so large that frictional heating will evaporate the adsorbed water and weakening will not occur. Content Type Journal Article Pages 1-10 DOI 10.1007/s00024-011-0324-0 Authors Charles G. Sammis, Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA David A. Lockner, US Geological Survey, Menlo Park, CA, USA Ze’ev Reches, School of Geology and Geophysics, University of Oklahoma, Norman, OK, USA Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553

Description:    Seismic coda wave attenuation ( Q \text c - 1 ) characteristics in the Garhwal region, northwestern Himalaya is studied using 113 short-period, vertical component seismic observations from local events with hypocentral distance less than 250 km and magnitude range between 1.0 to 4.0. They are located mainly in the vicinity of the Main Boundary Thrust (MBT) and the Main Central Thrust (MCT), which are well-defined tectonic discontinuities in the Himalayas. Coda wave attenuation ( Q \text c - 1 ) is estimated using the single isotropic scattering method at central frequencies 1.5, 3, 5, 7, 9, 12, 16, 20, 24 and 28 Hz using several starting lapse times and coda window lengths for the analysis. Results show that the ( Q \text c - 1 ) values are frequency dependent in the considered frequency range, and they fit the frequency power law ( Q \text c - 1 ( f ) = Q 0 - 1 f - n ). The Q 0 ( Q c at 1 Hz) estimates vary from about 50 for a 10 s lapse time and 10 s window length, to about 350 for a 60 s lapse time and 60 s window length combination. The exponent of the frequency dependence law, n ranges from 1.2 to 0.7; however, it is greater than 0.8, in general, which correlates well with the values obtained in other seismically and tectonically active and highly heterogeneous regions. The attenuation in the Garhwal region is found to be lower than the Q c −1 values obtained for other seismically active regions of the world; however, it is comparable to other regions of India. The spatial variation of coda attenuation indicates that the level of heterogeneity decreases with increasing depth. The variation of coda attenuation has been estimated for different lapse time and window length combinations to observe the effect with depth and it indicates that the upper lithosphere is more active seismically as compared to the lower lithosphere and the heterogeneity decreases with increasing depth. Content Type Journal Article Pages 1-18 DOI 10.1007/s00024-011-0316-0 Authors Jayant N. Tripathi, Department of Earth and Planetary Sciences, University of Allahabad, Allahabad, 211002 India Priyamvada Singh, Department of Earth and Planetary Sciences, University of Allahabad, Allahabad, 211002 India Mukat L. Sharma, Department of Earthquake Engineering, Indian Institute of Technology, Roorkee, 247667 India Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553

Description:    Temperature data from nine boreholes in the Carpathian orogen in Romania were used to obtain information on the ground surface temperature history (GSTH) in the last 250 years. The temperature measurements were taken with a thermistor probe (sensitivity in the 10 mK range) using the stop-and-go technique, at 10 m intervals, in the depth range of 20–580 m. The least squares inverse modelling approach of Tarantola and Valette (J Geophys 50:159–170, 1982 ) was used to infer the GSTH. Long-term air temperature records available from the Romanian weather station network were used as a comparison term for the first 100–150 years of the GSTH, and as a forcing function in a POM-SAT model that combines borehole temperature profiles (BTPs) and meteorological time series (surface air temperature, SAT) to produce information on the so-called pre-observational mean (POM). Results from a global circulation model for the Romanian area are incorporated in the discussion as well. Content Type Journal Article Pages 1-16 DOI 10.1007/s00024-011-0322-2 Authors Crisan Demetrescu, Institute of Geodynamics, Romanian Academy, Bucharest, Romania Maria Tumanian, Institute of Geodynamics, Romanian Academy, Bucharest, Romania Venera Dobrica, Institute of Geodynamics, Romanian Academy, Bucharest, Romania Constantin Mares, Institute of Hydrology, Bucharest, Romania Ileana Mares, Institute of Hydrology, Bucharest, Romania Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553

Description:    Tsunamis are high-impact disasters that can cause death and destruction locally within a few minutes of their occurrence and across oceans hours, even up to a day, afterward. Efforts to establish tsunami warning systems to protect life and property began in the Pacific after the 1946 Aleutian Islands tsunami caused casualties in Hawaii. Seismic and sea level data were used by a central control center to evaluate tsunamigenic potential and then issue alerts and warnings. The ensuing events of 1952, 1957, and 1960 tested the new system, which continued to expand and evolve from a United States system to an international system in 1965. The Tsunami Warning System in the Pacific (ITSU) steadily improved through the decades as more stations became available in real and near-real time through better communications technology and greater bandwidth. New analysis techniques, coupled with more data of higher quality, resulted in better detection, greater solution accuracy, and more reliable warnings, but limitations still exist in constraining the source and in accurately predicting propagation of the wave from source to shore. Tsunami event data collected over the last two decades through international tsunami science surveys have led to more realistic models for source generation and inundation, and within the warning centers, real-time tsunami wave forecasting will become a reality in the near future. The tsunami warning system is an international cooperative effort amongst countries supported by global and national monitoring networks and dedicated tsunami warning centers; the research community has contributed to the system by advancing and improving its analysis tools. Lessons learned from the earliest tsunamis provided the backbone for the present system, but despite 45 years of experience, the 2004 Indian Ocean tsunami reminded us that tsunamis strike and kill everywhere, not just in the Pacific. Today, a global intergovernmental tsunami warning system is coordinated under the United Nations. This paper reviews historical tsunamis, their warning activities, and their sea level records to highlight lessons learned with the focus on how these insights have helped to drive further development of tsunami warning systems and their tsunami warning centers. While the international systems do well for teletsunamis, faster detection, more accurate evaluations, and widespread timely alerts are still the goals, and challenges still remain to achieving early warning against the more frequent and destructive local tsunamis. Content Type Journal Article Pages 1-21 DOI 10.1007/s00024-011-0287-1 Authors Y. Igarashi, United Nations Educational, Scientific and Cultural Organization/Intergovernmental Oceanographic Commission (UNESCO/IOC) - NOAA International Tsunami Information Center, 737 Bishop St., Ste. 2200, Honolulu, HI 96813, USA L. Kong, United Nations Educational, Scientific and Cultural Organization/Intergovernmental Oceanographic Commission (UNESCO/IOC) - NOAA International Tsunami Information Center, 737 Bishop St., Ste. 2200, Honolulu, HI 96813, USA M. Yamamoto, UNESCO/IOC, 1 Rue Miollis, 75732 Paris Cedex 15, France C. S. McCreery, NOAA Pacific Tsunami Warning Center, Ewa Beach, Honolulu, HI 96706-2928, USA Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553

Description:    On 15 January 2010, Thumba (8.5°N, 76.9°E) witnessed one of the longest known noontime annular solar eclipses (ASEs) spanning a period of about 7 min, centered at 1314 hours local time. In this research article, we present a case study on the behaviour of the atmospheric boundary layer characteristics and its vertical structure in response to this rare celestial event by making use of a suite of different in-situ instruments. During the peak period of the ASE, the incoming solar irradiance was dimmed by about 87% of its normal values, resulting in a significant reduction in the magnitudes of turbulent kinetic energy and surface-layer turbulent fluxes of heat and momentum. The intensity and vertical thickness of the sea/land breeze circulation cell over the study domain also weakened. However, the mixed layer heights determined from balloon-borne GPS Radiosonde did not show any appreciable changes. Analysis of vertical profiles of thermodynamic parameters in association with the wind direction during ASE indicated the formation of a double mixed layer between 700 and 1500 m and is attributed to horizontal advection of a different airmass at those altitudes. Content Type Journal Article Pages 1-13 DOI 10.1007/s00024-011-0336-9 Authors D. Bala Subrahamanyam, Space Physics Laboratory, Vikram Sarabhai Space Centre, Department of Space, Government of India, Indian Space Research Organization, Thiruvananthapuram, 695 022 Kerala, India T. J. Anurose, Space Physics Laboratory, Vikram Sarabhai Space Centre, Department of Space, Government of India, Indian Space Research Organization, Thiruvananthapuram, 695 022 Kerala, India Mannil Mohan, Space Physics Laboratory, Vikram Sarabhai Space Centre, Department of Space, Government of India, Indian Space Research Organization, Thiruvananthapuram, 695 022 Kerala, India M. Santosh, Space Physics Laboratory, Vikram Sarabhai Space Centre, Department of Space, Government of India, Indian Space Research Organization, Thiruvananthapuram, 695 022 Kerala, India N. V. P. Kiran Kumar, Space Physics Laboratory, Vikram Sarabhai Space Centre, Department of Space, Government of India, Indian Space Research Organization, Thiruvananthapuram, 695 022 Kerala, India S. Sijikumar, Space Physics Laboratory, Vikram Sarabhai Space Centre, Department of Space, Government of India, Indian Space Research Organization, Thiruvananthapuram, 695 022 Kerala, India Journal Pure and Applied Geophysics Online ISSN 1420-9136 Print ISSN 0033-4553