The goal of this study is to determine whether principal component analysis (PCA) can be used to process latitude-time ionospheric TEC data on a monthly basis to identify earthquake associated TEC anomalies earlier than 5 days before a large (M ≥ 6) earthquake. PCA is applied to latitude-time (mean-of-a-month) ionospheric total electron content (TEC) records collected from the Japan GEONET system to detect TEC anomalies associated with 26 earthquakes in Japan (M ≥ 6.0) from 2004 to 2005. According to the results, PCA was able to discriminate clear TEC anomalies in the months when all 26 earthquakes occurred. After reviewing months when no M ≥ 6.0 earthquakes occurred but geomagnetic storm activity was present, it is possible that the maximal principal eigenvalues PCA returned for these 26 earthquakes indicate earthquake associated TEC anomalies. Previously, PCA has been used to discriminate earthquake-associated TEC anomalies recognized by other researchers who found that statistical association between large earthquakes and TEC anomalies could be established in the 5 days before earthquake nucleation; however, since PCA uses the characteristics of principal eigenvalues to determine earthquake related TEC anomalies, it is possible to show that such anomalies existed earlier than this 5-day statistical window. In this paper, this is shown through the application of PCA to one-dimensional TEC data relating to the Kyushu earthquake of 20 March 2005 (M = 6.6). The analysis is applied to daily TEC and reveals a large principal eigenvalue (representative of an earthquake associated anomaly) for March 9, 11 days before the March 20 earthquake.
Authors:E Juhásová, M Matys, J Frankovská, and P Labák
Application of local conditions in earthquake engineering is interconnected with the achievements in natural sciences like geology, seismology and geotechnics. Due to variation of soil conditions on the territory of Slovakia, the properties of response spectra and/or simulated or adapted recorded accelerograms should take these phenomena into account. The paper discusses the approaches to the determination of shear wave velocities and soil-structure interaction. Possible application of latest records from new Slovak seismic station network is discussed, too.
Many construction products contain asbestos. These are incorporated in the buildings in which we live. The term “asbestos” refers to six fibrous silicate materials that are naturally found in the Earth’s crust. It consists of many tiny fibers that can be seen only with a microscope. When products containing asbestos are disturbed, the asbestos fibers are broken into smaller pieces and these pieces float into the air even under the smallest air currents. Friable materials are therefore to be removed from buildings before demolition since they are considered hazardous waste, whereas non-friable materials may be normally treated as construction debris.Since asbestos represents material that is used in constructing floors, partition walls, thermal isolation, water and sewerage pipes, i.e., it represents part of the buildings, it is exposed to earthquake effect, as well.The present paper deals with the effect of earthquakes on asbestos plates and how this reflects the health of the population. Protection against these effects and regulations to be observed are also presented.
Authors:M. Zoran, R. Savastru, D. Savastru, C. Chitaru, L. Baschir, and M. Tautan
South-Eastern part of Romania has a highest potential seismic risk in Europe due to the earthquake-prone Vrancea zone placed
at conjunction of four tectonic blocks in the South-Eastern part of Carpathian Arc. This paper is an attempt to analyze the
development of radon pre-earthquake anomaly in relation with moderate seismic events in Vrancea area through permanent monitoring
with solid state nuclear track detectors CR-39 detectors. Radon in air above the ground was measured during 1 year period
(November 2010–October 2011) in four selected test sites: Vrancioaia (VRI) and Plostina (PLOR) located in Vrancea zone, and
Muntele Rosu-Cheia and Bucharest. During sampling period recorded earthquakes that occurred mostly in Vrancea epicentral region
were minor-moderate of moment magnitudes in range of
. The average radon concentration in air above the ground measured with CR-39 detectors and 10 days period recorded simultaneously
at all test sites, registered the following values: (1) in Vrancea area (similar in VRI and PLOR) was 1094.58
130 Bq/m3). Clear radon anomalies, mostly at VRI and PLOR in Vrancea epicentral area as well as at Muntele Rosu-Cheia have been measured
before seven minor earthquakes which were recorded in the range of moment magnitude
in Vrancea area. Temporal variation of radon in air near the ground have been examined in relation with meteorological parameters
like as air temperature, relative humidity, air pressure and wind velocity. Permanent monitoring of radon concentration anomalies
in seismic area Vrancea is an important issue as surveillance tool in the field of earthquake hazard for Romania.
Gamma-ray intensities were measured of the ground on an eastern part of the Kobe urban area, where a strong earthquake occurred in January 1995 killing 6000 people, in order to investigate hidden faults and its relation to the damage of constructions. Several linear alignments of relatively high -ray intensity points were detected and at least some of them are considered to be ascribed to small-scale faults. It can be pointed out that the localities of such high -ray alignments are almost in accordance with those of relatively highly damaged zones. However, a long and distinct high -ray alignment as expected for a large fault which runs through the heavy damage belt does not exist beneath the area, supporting non-fault origin for the overall heavy damage belt.
This research uses Principal Component Analysis (PCA) to investigate global ionospheric integrated electron content map (GIM) anomalies corresponding to Japan’s Iwate-Miyagi Nairiku earthquake on 13 June 2008 (UT) (Mj = 7.2, JMA scale). The PCA transform is applied to GIMs for 20:00 to 22:00 on June 08, 11 and 12, 2008 (UT). To perform the transform, image processing is used to subdivide the GIMs into 100 (36° long. and 18° lat.) smaller maps to form transform matrices of dimensions 2 × 1. The transform allows for principal eigenvalues to be assigned to ionospheric integrated electron content anomalies. Anomalies are represented by large principal eigenvalues (i.e., >0.5 in a normalized set). The possibility of geomagnetic storms and solar flare activity affecting the results is done through examining the Dst index for corresponding days. The study shows that for the Iwate-Miyagi Nairiku earthquake, PCA possibly determined earthquake related ionospheric disturbances for the whole region, including the epicenter.
In the seismic source zone of Bánát more than 600 earthquakes are known since 1773 among them six events with magnitude of 5.0–5.7 measured on the surface magnitude scale. The macroseismic reinterpretation of the April 2, 1901 earthquake yields epicentral intensity of VII on the European Macroseismic Scale, and a focal depth value of 12 km. Based on empirical relations the maximum rupture area is estimated as 50–55 km
and the maximum displacement along the fault is about 16 cm in the Bánát seismic zone due to the
= 5.7 event occurred on July 12, 1991. The average recurrence that we may expect an earthquake of
≥ 3.4 every 1 year, an earthquake of
≥ 4.3 every 10 years and an earthquake of
≥ 5.3 every 100 years in the studied source zone. The probabilistic seismic hazard assessment predicts 1.3–2.1 m/sec
peak ground accelerations, and 6.7–7.3 maximum (theoretical) earthquake intensity values with 10% chance of exceedance for an exposure time of 100 years in the region.
Ricles J.M., Sause R., Peng S.W., Lu L.W. Experimental evaluation of earthquake resistant posttensioned steel connections,
ASCE Journal of Structural Engineering
, Vol. 128, No. 7, 2002, pp. 850–859.
Authors:V. Singh, D. Shanker, H. Singh, and M. Banerjee
Seismically Kutch peninsula is very active. The distribution of seismicity in Peninsular Shield region from 1902 to 2001 show 12 earthquakes of
≥ 6. The energy ratio from Kutch basin to Deccan trap is 20:1 and from trap to rest of the shield is 5:1. The last one hundred years seismicity data show Kutch basin is seismically more active than Deccan trap and the rest of the Peninsular Shield. The maximum magnitude of earthquake in the Kutch region is 7.7. The generations of large earthquakes in the region are difficult to explain, as plate boundary does not exist. In order to understand the physical processes that are taking place in the region to generate such large events the detailed analyses of geophysical and geological data have been examined in the light of development of rift, subsidence of basin, vertical tectonics and recent geophysical findings. In such regions, petrologic model can provide better explanation for release of fluid that generates large earthquakes, sprouting of sands, liquefaction, and large number of aftershocks activities and direction of stresses for aftershock sequences. The presence of magma in the Kutch upper mantle could be derived from various geological (subsidence of basin, development of rift faults) and geophysical observations (high heat flow over Cambay region, prominent positive Bouguer gravity anomalies and low shear velocity in the upper mantle). The inspection of seismological data shows all the medium size to large earthquake have occurred in shear zone of large gravity gradients or along the four major faults of the region. In view of geological and geophysical observations, petrologic model is proposed for generation of earthquakes in the region. The number of aftershocks and direction of stresses in the focal region of aftershocks would depend on the direction of movement of fluid incursion in the focal region after the occurrence of the main events. The recent Bhuj earthquake also shows more than 3000 aftershocks from Jan 29 to April 15, 2001. The expanding swarm activity in the focal region and the direction of stresses derived from first motion data of aftershocks for focal depths 2 to 8 km, 8 to 25 km, and 25 to 38 km supports the proposed model. Also, shear wave tomography studies in this region have revealed low shear wave velocity in the upper mantle of Cambay from shallow depth to 200 km depth showing high temperature zone. The analyses reveal the presence of conducting fluid in the focal zone, which is the main cause for generation of medium size to large earthquake in the region.
The original purpose of this investigation started in 1996 was to study the radiological impact on the local population of
the village of Chichiviriche de La Costa. But, soon after the major earthquake (Ms=6.8) in the state of Sucre on July 9, 1997,
the objective was changed to study the fluctuation of radon (222Rn) to see if it could be correlated to seismic activity and/or if the amonlous change just before the earthquake can be considered
a precusor for it. Measurements of222Rn by simply de-gassing about 250 ml of natural thermal water employing a Pylon AB-5 radiation monitor and counting the radiation
after it reached equilibrium were performed. The values for four sampling periods in the first half of 1996 were about 17
Bq/l of222Rn, a month before the earthquake they were less than 15 Bq/l and increased about 70% to 25 Bq/l two days before the seismic
event. In about two weeks, they returned to about 18 Bq/l. But, surprisingly, they have gradually increased to about 35 Bq/l,
before leveling off at about 27 Bq/l.