Microseismic anomalies before the Sumatra earthquake of December 26, 2004 (original) (raw)
Related papers
Asymmetrical pulses, the periodicity and synchronization of low frequency microseisms
Journal of Volcanology and Seismology - J VOLCANOL SEISMOL, 2008
Seismic records of eight IRIS broadband stations were analyzed at distances of 70 to 7160 km from the magnitude 8.3 Hokkaido earthquake of September 25, 2003. The stations situated in the subduction zone recorded asymmetrical microseismic pulses lasting 3–10 min a few days before the earthquake. No such pulses were observed in the records of the stations situated outside the subduction zone. Similar pulses were also recorded before the magnitude 7.8 Kronotskii, Kamchatka earthquake of 1997. The pulses are hypothesized to have been caused by creeping movements. Synchronous oscillations of microseismic noise with periods of 1–3 h were recorded as far as 3000 km from the Hokkaido earthquake a few days before it occurred. The noise coherence measure increased for stations closer to the epicenter. The question of the source of this coherence remains open. These effects belong to the class of those occurring in dissipative metastable systems; parts of the terrestrial lithosphere during th...
The statistics of the time segments of low-frequency microseisms: Trends and synchronization
Izvestiya, Physics of the Solid Earth, 2010
The problem of identifying the effects of synchronization in the parameters of low frequency microseismic noise from the data of 77 stations belonging to the F net broadband seismograph network in Japan for the period from the beginning of 1997 through August, 2009 is considered. The vertical components measured initially with a sampling rate of one second and subsequently converted into the signals sampled at 1 minute intervals by means of averaging and decimation are used in the analysis. Six statistics are taken as the parameters: the support width of the multifractal singularity spectrum; the generalized Hurst exponent; the asymmetry coefficient of the spectrum of singularity; the logarithmic variance; the spectral exponent; and the linear predictability index. These parameters are calculated from the realizations contained within con secutive daily time intervals. When using the moving time window with a width of one year for evaluating the multiple correlation, the daily variations in the median values of the statistics of the noise measured at five spatial clusters of stations exhibit a stable increase in the synchronization not long before the Hokkaido earth quake (September 25, 2003; M = 8.3), subsequently passing to the new level of high synchronization. Based on the analysis of the trends in the index of linear predictability it turned out possible to estimate the begin ning of the enhancement in the synchronization with rather high accuracy as the middle of 2002. The effect revealed for the variations in the different parameters of microseisms is an independent argument for the ear lier conclusion about the synchronization in the field of the microseismic noise on the Japan Islands.
Izvestiya, Physics of the Solid Earth, 2008
The paper generalizes the experience accumulated in studies of microseismic noise in the period range from 1 to 300 min observed during time intervals preceding a few strong earthquakes. This frequency range is the least studied and occupies an intermediate position between low frequency seismology and investigations of slow geophysical processes. The range includes oscillations induced by atmospheric and oceanic processes and various modes of the Earth's free oscillations excited by very strong earthquakes. The main attention in the paper is given to the background behavior of microseisms, which contains continuous present arrivals from near weak and far strong and moderate earthquakes. The paper focuses on the examination of synchronization effects arising in joint multivariate analysis of information from several stations with estimation of multifractal spectra of singularity and multidimensional spectral measures of coherent behavior of singularity spectral parameters. The problem of using the synchronization effects of microseismic background in the search for new precursors of strong earthquakes is discussed. PACS numbers: 91.30.Bi
Synchronization of Microseismic Variations within a Minute Range of Periods
Izvestiya Physics of the Solid Earth
Records obtained at the Petropavlovsk, Yuzhno-Sakhalinsk, Magadan, Yakutsk, and Obninsk IRIS broadband stations before the Kronotski (Kamchatka) earthquake are investigated with the use of various programs of processing and analysis of time series. Intervals of a stable manifestation of one or several periods of microseisms (synchronization intervals) inferred from data of different stations do not necessarily coincide in time. No anomalous meteorological effects are recorded in these intervals. Geodynamic phenomena on global and regional scales influence the duration and intensity of the synchronization intervals. As distinct from other stations, the Petropavlovsk record revealed asymmetric variations of the relaxation type that arose five days before the Kronotski earthquake and three days before the onset of intense foreshock activation. The amplitude of variations at this station exceeds the level of other stations by an order of magnitude, which indicates that the source of this earthquake was located in the Pacific seismically active region. The number of predominant periods at the Petropavlovsk station decreases toward the time moment of the Kronotski earthquake, and the polymodal spectrum becomes unimodal, primarily due to the loss of shorter periods: a period of 37 min is most clearly expressed 1 h before the earthquake. The synchronization intervals of variations, as well as the foreshock activation, are indicators of the unstable state of a seismically active region.
Izvestiya, Physics of the Solid Earth, 2009
The field of low-frequency microseisms is investigated with the use of data from 83 stations of the F-net broadband network in Japan over the period from the beginning of 1997 through June 2008. Vertical components with a sampling step of 1 s are used for analysis, as well as signals with a sampling step of 1 min obtained from the initial data by averaging and thinning. Long-period regularities of changes in the singularity spectrum support width ∆α and the generalized Hurst exponent α * for the field of low-frequency microseisms were revealed by estimating multifractal singularity spectra in consecutive time windows 30 min long for 1-s data and 24 hour long for 1-min data. The average value of the parameter ∆α for 1-s data significantly decreased before the Hokkaido earthquake of September 25, 2003 ( M = 8.3), and was not restored subsequently to its previous level. Prior to September 2003, 1-min data on α * variations experienced strong annual changes, which completely ceased afterwards. Both these effects are interpreted as an increase in the degree of synchronization of microseismic noise on Japan's islands after the September 25, 2003, earthquake. This hypothesis is also supported by estimates of the measures of correlation and spectral coherence between variations in the average values of ∆α and α * calculated for 1-min data inside five spatial clusters of stations from consecutive time fragments two months long. Based on the well-known statement of the theory of catastrophes that synchronization is one of the flags of an approaching catastrophe, it was suggested that the Hokkaido event could be a foreshock of an even stronger earthquake nucleating in the region of Japan's islands. PACS numbers: 91.30.Ab
A note on the 26 December 2004 great Sumatra earthquake
2005
is operating broadband seismic stations in different parts of India. The stations are equipped with latest generation seismometers with high sensitivity like CMG-40T, CMG-3ESP. The data acquisition systems have high dynamic range (144dB), achieved by a 24-bit digitizer and recorded at 100 samples per second. This earthquake was recorded at Hyderabad. Cuddapah, Kothapudeh. Naldurg in southern peninsular India. at stat~ons of Tezpur selsmlc network in Northeast India and at stations of Koyna seismic network in Western India Surface waves are clipped at most of the stations (except at Kothagudem and Cuddapah where the seismometer is CMG-40T), which dld not allow us to estimate earthquake parameters uslng surface waves. The nearest NGRI seismic station to record this event is at an epicentral distance of about 2230 km. Waveforms recorded at NGRI se~smic stations are shown in Fig. 1.
2009
Passive low frequency microseismic experiment has been carried out over the Tambun-oilfield, West Java, Indonesia. Five sensitive 3-component broadband seismometers with sensitivity of 1500 V/m/s have been used to measure more than 50 points along two different profiles across the reservoir (about 15 km profile length) and over the production wells. We perform a polarization analysis to discriminate the hydrocarbon microseismic data with local ambient noise using high-dip and high-linearity criterion. Spectral analysis was applied for hydrocarbon microseismic signals with frequency range from 0.5 to 7 Hz. The power spectral density anomaly was plotted over the structural map of the Tambun-oilfield. A good correlation between microseismic spectral anomaly (from 2 Hz to 4 Hz) and the production well clusters position and the known reservoir area was observed.
Geoplanet: Earth and Planetary Sciences, 2010
Nearly all models of earthquake preparation are known to indicate magnification of the collective component in the behavior of geophysical fields in the preparation zone as the moment the earthquake occurrence is approached. The geophysical monitoring is aimed at the detection of the so-called synchronization signal in variations of different geophysical parameters, as well as its duration and frequency range.
Microseismic research using coherence and cross-correlation in Depok, Sleman, Yogyakarta
IOP Conference Series: Earth and Environmental Science
Yogyakarta area is one of earthquake-prone area in Indoneis. It is include in the Indo-Australian plate subduction zone under the Eurasian plate. It also has an active fault, namely Opak fault that located in Bantul Regency. Microseismic method is one way that can be used to analyze soil vulnerability of earthquakes. The Microseismic method is a geophysical method that utilizes natural vibrations as its source. The data of the Microseismic Method is processed using HVSR Method. It is used to compare horizontal to vertical spectra ratio. The results of HVSR shows the value of the dominant frequency (f0), amplification (A0) the Soil Vulnerability Index (Kg). The results of this research that especially located in Depok District, Sleman Regency has the dominant frequency value that range from 0.65 to 1.35 Hz, amplification value between 2.6 and 5.6 and soil susceptibility value is 4-52 s 2 / cm. The data obtained from the southern part of the research area, it shows that it has dominant frequency and high amplification values. To reassure the data, coherence graphs, phase velocity graphs and cross correlation maps were made between amplification maps with dominant frequencies, dominant frequency maps with topography, amplification maps with topography and maps of soil vulnerability index with topography. Coherence and correlation cross graphs show a small link to the south of the research area.