Earthquake Of June Research Articles

A geodetic study of the 2003 January 22 Tecomán, Colima, Mexico earthquake

We use coseismic displacements and aftershock information from Global Positioning System (GPS) measurements at 27 sites in western Mexico and a 12-station local seismic network to determine the characteristics of the 2003 January 22 M_w = 7.2 subduction thrust earthquake near Tecoman, Colima, Mexico. Estimates of the earthquake moment, slip direction and best-fitting slip distribution are derived by optimizing the fit to the GPS displacements for a 3-D finite element mesh that simulates the study area. The calculated moment release is 9.1 × 10^(19) N m (M_w = 7.2) , with maximum slip of 2 m at a depth of 24 km and a maximum rupture depth of 35–40 km. The inversion indicates that coseismic rupture extended downdip from depths of 9 to 40 km along a 80 km along-strike region that is bounded by the edges of the Manzanillo Trough. The optimal solution is robust with respect to plausible changes in the subduction interface geometry and differing subsets of the data. A comparison of the cumulative post-seismic slip that can be inferred separately from earthquake aftershocks and GPS measurements within a year of the earthquake indicates that 95 per cent or more of the post-seismic deformation was aseismic. Near-term post-seismic measurements indicate that slip propagated downdip to areas of the subduction interface beneath the coastline within days following the earthquake, as also occurred after the nearby M_w = 8.0 Colima-Jalisco subduction earthquake in 1995. The similar behaviours and locations of the 1995/2003 earthquake sequence to two earthquakes in June of 1932 suggests that thrust earthquakes along the subduction interface northwest of the Manzanillo Trough may trigger earthquakes in the vicinity of the Manzanillo Trough; however, our modelling of Coulomb stress changes caused by the 1995 earthquake indicate that it induced only modest unclamping of the subduction interface in the vicinity of the Tecoman rupture. In addition, GPS measurements indicate that elastic shortening characterized areas onshore from the Tecoman rupture from mid-1997 up until the time of the rupture, consistent with progressively stronger clamping of the subduction interface during this period. This precludes any obvious triggering relationship with the 1995 earthquake. The apparent coincidence of the edge of both the 1932 and 1995/2003 rupture sequences with the edge of the Manzanillo Trough may indicate that the trough is a mechanical barrier to along-strike rupture propagation. This implies a limit to the area of potential slip and hence rupture magnitude during future large earthquakes in this region.

The seismic and hydroacoustic stations on Socorro Island: Early results


 
 
 A seismic and hydroacoustic network on Socorro Island was installed jointly by the Servicio Sismolo?gico Nacional, Instituto de Geofi?sica, Universidad Nacional Auto?noma de Me?xico, and the Comprehensive Nuclear-Test-Ban Treaty Organization. The detection of ten earthquakes in June and July 2004 is reported in this study. These events occurred at epicentral distances between 209 and 9050 km and ranged in magnitude between 3.9 and 6.8. An event in the Kamchatka Peninsula featured arrivals of teleseismic high-frequency P and pP waves from a distance of 8245 km. An earthquake in the Guerrero-Oaxaca, Mexico, region shows clear seismic and T phases. Three earthquakes in the Rivera Fracture Zone were recorded, thus leading to the expectation of the continued detection of events from nearby fracture zones as well as earthquakes generated by volcanoes on Socorro and San Benedicto Islands. The analysis of the T phases from several events validates the design of the network, with three sites around the island in order to record arrivals from all directions. High frequency seismic waves generated by acoustic waves attenuate as they propagate through the rock from one end of the island to the other. Consequently small or distant events are difficult to detect at the far side of the island.
 
 

Current plate movements across the Mid‐Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland

We analyze data spanning up to 5 years from 18 continuous GPS stations in Iceland, computing daily positions of the stations with three different high‐level geodetic processing software packages. We observe large‐scale crustal deformation due to plate spreading across Iceland. The observed plate divergence between the North American and the Eurasian plates is in general agreement with existing models of plate motion. Spreading is taken up within a ∼100–150 km wide plate boundary zone that runs through the island. Of the two parallel branches of the plate boundary in south Iceland, the eastern volcanic zone is currently taking up the majority of the spreading and little is left for the western volcanic zone. The plate boundary deformation field has been locally and temporarily affected in south Iceland by two Mw = 6.5 earthquakes in June 2000, inflation at Katla volcano during 2000 to 2004, and an eruption of Hekla volcano in February 2000. All stations with significant vertical velocities are moving up relative to the reference station REYK, with the highest velocity exceeding 20 mm/yr in the center of the island.

Landslides triggered by the Avaj, Iran earthquake of June 22, 2002

The 2002 Avaj, Iran earthquake (Mw = 6.5) triggered many landslides over an area of about 3600 km 2. In this paper, we describe a ground-based field study conducted during several days immediately after the earthquake, and pre and post-earthquake landslide inventory maps that were prepared. The landslides due to earthquake include 47 fall and topple zones, 9 slides, and 3 lateral spreads. The largest slide is a rockslide (150 × 100 m), which occurred southeast of the village of Changureh. The main results of this study are: • The density of earthquake triggered landslides decreases away from the fault zone in a manner that is asymmetric with respect to direction; • Although several slides and lateral spreads were seen, the most common types of triggered landslides are falls and topples; • The area throughout which landslides occurred, and maximum epicentral and fault zone distances of landslides, are comparable to similar data from other historical earthquakes; • Landslides mostly occurred in the most susceptible geologic units, in which there were many landslides before the earthquake; • New disrupted slides and falls generally occurred in ancient fall zones, but no information about reactivation of coherent slides is available.

Macroseismic and instrumental data comprehensive analysis: Earthquake of June 2, 1930 in Catalonia (Spain)

Macroseismic and instrumental data comprehensive analysis: Earthquake of June 2, 1930 in Catalonia (Spain)

New determinations of Q quality factors and eigenfrequencies for the whole set of singlets of the Earth's normal modes 0S0, 0S2, 0S3 and 2S1 using superconducting gravimeter data from the GGP network

Abstract We present new modal Q measurements of the 0 S 0 and 0 S 2 modes, and first modal frequencies and Q measurements of 2 S 1 and 0 S 3 modes. The high quality of the GGP (Global Geodynamics Project) superconducting gravimeters (SGs) contributes to the clear observation of seismic normal modes at frequencies lower than 1 mHz and offers a good opportunity for studying the behaviour of these modes. The interest of scientists in the gravest normal modes is due to the fact that they do contribute to a better knowledge of the density profile in the Earth, helping to constrain Earth's models. These modes have been clearly identified after some large recent events recorded with superconducting gravimeters, particularly well-suited for low-frequency investigations. The Ms = 8.1 (Mw = 8.4) Peruvian earthquake of June 2001 and the Ms = 9.0 (Mw = 9.3) Sumatra-Andaman earthquake of December 2004 provide us with individual spectra which exhibit a clear splitting of the spheroidal modes 0 S 2 , 0 S 3 and 2 S 1 , and a clear identification of each of the individual singlets, with a resolution never obtained from broad-band seismometers records. The Q quality factors have been determined from the apparent decrease of the amplitude of each singlet with time, according to a well-suited technique [Roult, G., Clevede, E., 2000. New refinements in attenuation measurements from free-oscillation and surface-wave observations. Phys. Earth Planet. Inter. 121, 1–37]. The results are compared to the theoretical frequencies and Q quality factors computed for the PREM and 1066A models, taking into account both rotation and ellipticity effects of the Earth. The two observed datasets (frequencies and Q quality factors) exhibit a splitting on the observed values different from the predicted one. That seems to point out that some parameters as density or attenuation values used in the theoretical models do not explain the observations. A new dataset of frequencies and Q quality factors of the whole set of singlets of the gravest spheroidal modes is thus under construction. That dataset includes the five individual singlets of the 0 S 2 mode clearly identified on the SG records, the three singlets of the 2 S 1 mode recently observed for the first time by [Rosat, S., Hinderer, J., Rivera, L., 2003b. First observation of 2 S 1 and study of the splitting of the football mode 0 S 2 after the June 2001 Peru earthquake of magnitude 8.4. Geophys. Res. Lett. 30, 21211, doi:10-1029/2003L018304], the 0 S 0 radial mode, and the seven individual singlets of the 0 S 3 mode.

The Social Content of Damage-Rating or: Fictions of Earthquake Reconstruction. Benevento after the Earthquake of June 5th, 1688

The evaluation of earthquake intensities is one of the most important aims of historical seismology. This article argues, that historical data of earthquake damages are less then data, but facta. The earthquake of June 5^th, 1688 in Benevento, enclave of the Papal State in the Kingdom of Naples, and the following reconstruction of buildings with subsidies of pope Innocent XI. Odescalchi illustrates, that financial assistance and reconstruction are by no means value free or inspired by equality, but reflect the social conditions of the society coping with reconstruction. As a consequence historical data of damages and reconstruction are determined by these social conditions and are not “objective figures“ but social (and scientific) fictions.

Southern Peru desert shattered by the great 2001 earthquake: Implications for paleoseismic and paleo-El Niño–Southern Oscillation records

In the desert region around the coastal city of Ilo, the great southern Peru earthquake of June 23, 2001 (8.2-8.4 moment magnitude), produced intense and widespread ground-failure effects. These effects included abundant landslides, pervasive ground cracking, microfracturing of surficial hillslope materials, collapse of drainage banks over long stretches, widening of hillside rills, and lengthening of first-order tributary channels. We have coined the term "shattered landscape" to describe the severity of these effects. Long-term consequences of this landscape shattering are inferred to include increased runoff and sediment transport during postearthquake rainstorms. This inference was confirmed during the first minor postearthquake rainstorm there, which occurred in June and July of 2002. Greater amounts of rainfall in this desert region have historically been associated with El Niño events. Previous studies of an unusual paleoflood deposit in this region have concluded that it is the product of El Niño-generated precipitation falling on seismically disturbed landscapes. The effects of the 2001 earthquake and 2002 rainstorm support that conclusion.

Precursory behavior of fractal characteristics of the ULF electromagnetic fields in seismic active zones before strong earthquakes

It is now recognized that the earthquake hazard systems evolve naturally to the self-organized critical (SOC) state, in which the system is very sensitive to any external perturbations, and when the large avalanches (strong earthquakes) are probable events. Since the principal feature of the SOC state is fractal organization of the output parameters both in space (scale-invariant structure) and in time (flicker noise or 1/ f noise) we can use fractal methods to investigate the evolutionary processes in the earthquake hazard system at different stages of the catastrophic event preparation. Here we apply fractal methods for extraction of earthquake precursory signatures from ULF ( f=0.001–1 Hz) geomagnetic data obtained in seismic active regions before strong earthquake events. We focus our attention on the massive Guam earthquake of August 8, 1993 ( M=8, depth=60 km), and on a swarm of Japanese earthquakes of June–August 2000 occurred near Izu Peninsula ( M>6, depth ≈ 10 km). We analyze scaling (fractal) characteristics of ULF geomagnetic fields registered in the area less than 100 km from the earthquake epicenters, study their dynamics as approaching the earthquake dates, and compare the results obtained in both regions. Three methods have been applied to calculate scaling parameters (spectral exponents and fractal dimensions of the ULF geomagnetic time series): FFT procedure, Burlaga–Klein approach and Higuchi method. It is found that fractal characteristics of the ULF emissions manifest specific precursory behavior with some common and individual peculiarities in both seismic active areas. As the common feature, we have revealed the same increase of the ULF time series fractal dimensions (and the corresponding decrease of spectral exponents) before the both events. As the distinctive peculiarity, we have found different character of such dynamics: gradual increase (decrease) in the case of the Guam earthquakes and relatively sharp alteration in the case of the Izu earthquake swarm. For the case of Japanese earthquakes, it turned out to be possible to reveal the most effective frequency range (around f=0.01 Hz), in which precursory behavior of fractal characteristics is more pronounced and manifested earlier than in the other frequency ranges. We give a physical interpretation of the peculiarities revealed taking into account possible specifics of the SOC processes at different depths of the earthquake focuses.

Seismicity in Iceland during 2001

Over 14,000 earthquakes were located in 2001 by the SIL seismic system. During the first half of the year the majority of the located earthquakes were aftershocks of the magnitude 6.6 earthquakes of June 2000. The M˝rdalsjokull region was more seismically active than usual in the first half of the year and the Reykjanes ridge was fairly active in the latter half of the year. Many small earthquake swarms occurred as well, the two largest along the Tjornes Fracture Zone, offshore northern Iceland. The larger of these swarms originated in Oxarfjor﷿ur with a total number of earthquakes greatly exceeding previous swarms in the area, recorded by the SIL system. Five stations were added to the SIL network and one station was dismantled. At the end of the year 42 seismic stations comprised the SIL network.

Fractal analysis of the ULF geomagnetic data obtained at Izu Peninsula, Japan in relation to the nearby earthquake swarm of June–August 2000

Abstract. In our recent papers we applied fractal methods to extract the earthquake precursory signatures from scaling characteristics of the ULF geomagnetic data, obtained in a seismic active region of Guam Island during the large earthquake of 8 August 1993. We found specific dynamics of their fractal characteristics (spectral exponents and fractal dimensions) before the earthquake: appearance of the flicker-noise signatures and increase of the time series fractal dimension. Here we analyze ULF geomagnetic data obtained in a seismic active region of Izu Peninsula, Japan during a swarm of the strong nearby earthquakes of June–August 2000 and compare the results obtained in both regions. We apply the same methodology of data processing using the FFT procedure, Higuchi method and Burlaga-Klein approach to calculate the spectral exponents and fractal dimensions of the ULF time series. We found the common features and specific peculiarities in the behavior of fractal characteristics of the ULF time series before Izu and Guam earthquakes. As a common feature, we obtained the same increase of the ULF time series fractal dimension before the earthquakes, and as specific peculiarity – this increase appears to be sharp for Izu earthquake in comparison with gradual increase of the ULF time series fractal dimension for Guam earthquake. The results obtained in both regions are discussed on the basis of the SOC (self-organized criticality) concept taking into account the differences in the depths of the earthquake focuses. On the basis of the peculiarities revealed, we advance methodology for extraction of the earthquake precursory signatures. As an adjacent step, we suggest the combined analysis of the ULF time series in the parametric space polarization ratio – fractal dimension. We reason also upon the advantage of the multifractal approach with respect to the mono-fractal analysis for study of the earthquake preparation dynamics.

Rapid ground deformation of the Miyakejima volcano on 26–27 June 2000 detected by kinematic GPS analysis

A kinematic GPS analysis of data from the Miyakejima volcano captured a fast developing deformation event on 26–27 June 2000 in unprecedented spatial and temporal detail. Initial ground deformation toward east and upward was observed in the southeastern part of the volcano at 18:00 on 26 June 2000, almost simultaneous with earthquake swarms. Some time after 21:30 on 26 June 2000 the displacements at these sites turned from eastward to westward. Three hours later the displacement rates increased gradually at GPS sites in the western part of Miyakejima as the seismicity migrated and approached the west coast, and reached a climax with submarine eruption at 09:00 on 27 June 2000. A Genetic Algorithm was used to explore the parameter space and to find the best fitting source geometry. This analysis leads to an interpretation that the 18:00 26 June earthquake swarm was caused by a dike intrusion near the Oyama crater. Starting from 21:30 this dike deflated and a new dike intruded near the west coast. Following the propagation of this dike to the offshore, a spherical source began deflating in the southwest of Oyama crater.

Coulomb stress changes in the South Iceland Seismic Zone due to two large earthquakes in June 2000

The South Iceland Seismic Zone experienced the largest earthquakes for 88 years in June 2000, with a MS = 6.6 event on June 17, followed by another MS = 6.6 earthquake on June 21. These events occurred on two parallel N‐S striking, right‐lateral strike slip faults, separated by about 17 km. We calculate the static Coulomb stress change for the June 17 and 21 earthquakes using a distributed slip model derived from joint inversion of InSAR and GPS data. We find that the static stress change caused by the June 17 event is about 0.1 MPa at the location of the June 21 hypocenter, promoting failure on the second fault. Locations of aftershocks agree well with areas of increased Coulomb failure stress. Our calculations indicate that positive stress changes due to the two earthquakes make the area west of the June 21 rupture the most likely site of the next large earthquake in South Iceland.

Estimation of causative fault parameters of the Rudbar earthquake of June 20, 1990 from near field SH-wave data

We analyze the strong motion accelerograms recorded for the large (MS=7.7, MW=7.3, mb=6.4) Rudbar earthquake of June 20, 1990. The earthquake had a complex source process. We have identified the imprints of rupture of three localized asperities on the major causative fault on the accelerograms. These asperities are interpreted to correspond to (i) the main shock that initiated the rupture process and was located in the domino block between the Kabateh and Zard Goli faults, (ii) a foreshock that occurred about 10 s earlier in the Kabateh fault and (iii) a later shock, on the western end of the Baklor fault, which terminated the bilateral rupture process at the western end. We estimate the strike, dip and slip of these causative sub-event rupture planes using the SH spectral amplitudes, based on a point source representation of sub-events and a non-linear least square formulation for inversion of the amplitude data. The results of our inversion of the near field data are comparable to other studies based on teleseismic data.

Seismic regime of Southern California in relation to the crustal rigidity variations

The Landers (southern California) destructive (M = 7.3) earthquake of June 28, 1992 had epicentral coordinates of (34.2 N, 116.44 W) and was a major seismic event of the period from 1985 through 2002. It was examined in many papers, mostly published in a special issue of Bulletin of Seismological Society of America (BSSA) of June 1994 (vol. 84, no. 3). The majority of the works were devoted to phenomena related to the earthquake itself and its eects. The present paper presents the results derived from the analysis of rigidity variations at the preparation stage of the main shock. This analysis was based on a method developed by the authors for the monitoring of rigidity variations in the seismically active layer of the crust. The method reduces to the possibility of discriminating between the brittle and viscous failure modes using P wave first arrival patterns.

A detailed source study of the Orta (Çankırı) earthquake of June 6, 2000 (MS = 6.1): An intraplate earthquake in central Anatolia

The devastating Izmit and Duzce earthquakes were followed by theOrta intra-plate earthquake (MS = 6.1) occurred in the central Anatolianblock on June 6, 2000. The focal mechanism, aftershock distribution andthe field studies (Emre et al., 2000) suggest a movement on a 21-km longDodurga fault striking nearly N-S where the sense of motion is left-lateralstrike-slip with considerable amount of normal component. We applied theconstrained linear finite-fault inversion method of Hartzell and Heaton(1983) to the teleseismic P and SH waveforms to derive a coseismic slipdistribution model for the earthquake. Time windows approach is appliedallowing variable rise times and rupture velocities. The source-rise timefunction is discretized into consecutive time intervals that stand for slipcontribution of individual subfaults. Although no clear surface ruptureswere associated with the earthquake, the resulting slip model suggestscoseismic slip in the order of several tens of centimetres. Our coseismicslip distribution model identifies two slip patches with the followingmaximum slip values: (1) the larger one (42 cm) is located to the southof the hypocenter at depth range of 4–8 km and (2) the smaller one(31 cm) is located just above and north of the hypocenter. Theslip-model yield a seismic moment of 1.0 × 1018 Nm, most of whichis released from the rupture over the depth of 8 km.

The June 2000 Mw 7.9 earthquakes south of Sumatra: Deformation in the India–Australia Plate

Two large (Mw 7.9) earthquakes occurred on 4 and 18 June 2000, south of Sumatra, beneath the Indian Ocean. Both earthquakes were predominantly left‐lateral strike‐slip on vertical N‐S trending faults that we interpret to be reactivated fracture zones. The 4 June Enggano earthquake occurred at the edge of the rupture area of the 1833 subduction earthquake. The first strike‐slip subevent within the subducting plate triggered a thrust subevent on the plate interface, which comprised at least 35% of the total moment and ruptured SE away from the 1833 earthquake. The 18 June earthquake in the Wharton Basin is one of the largest shallow strike‐slip faulting earthquakes ever recorded. A small second subevent with reverse slip is required to fit the body waves. The orientation of both subevents in our preferred model is consistent with the current stress field in the region. Both the June 2000 earthquakes are consistent with recent models of distributed deformation in the India–Australia composite plate. The occurrence of the Enggano earthquake implies that the stress field within the Indian plate continues to a depth of 50 km in the subducting slab. The purely strike‐slip source model of the Wharton Basin earthquake obtained by Robinson et al. [2001] matches the P waves very poorly and fits the S waves no better than our preferred model. The strike‐slip subevents of both earthquakes had few aftershocks and higher stress drops than the subduction thrust subevent of the Enggano earthquake. This difference is consistent with previous observations of oceanic and subduction earthquakes.

Sustainable Cities, a Regional Seismic Scenario, and the 6-23-2001 Arequipa Peru Earthquake

From 1998 to early 2001, fifteen Peruvian cities developed and enforced ordinances on land use, channeling urban expansion and population growth into areas that microzonation investigations had determined to be safe. This process took place as part of the Sustainable Cities, First Stage (SC-1S). The hazard maps, land use planning, and priority projects to reduce the vulnerability of the city facilities were unanimously approved by the communities involved and all local government council members. Investigations into the effects of the Arequipa, Peru, earthquake of June 23, 2001, were performed to take advantage of this unique opportunity to find out just how useful pre-event studies are in reducing disasters. In this case a regional seismic scenario (RSS) had been constructed from 1992 to 1995 for Peru's southwestern region. The macroseismic area of the June 2001 event overlapped substantially with this RSS. The other main objective of the comparison between the RSS and the effects of the real event was to validate the application of hazard maps in land use planning to reduce losses caused by intense natural events. It was estimated that relatively low acceleration on rock occurred over extensive areas, but this was greatly amplified on soft water-saturated soil, unstable slopes, and uncompacted filled soil. As those were the places where the RSS assumed that the earthquake damage would be severe, the predicted locations of the RSS coincided with the locations that were the worst hit by the June 2001 earthquake. In this paper, comparison is made between the 1992-1995 RSS and the effects of the Arequipa June 2001 earthquake, to verify how useful predisaster investigations are and to validate the seismic hazard maps employed in land-use planning for disaster reduction, which have been widely applied in Peru in the SC-1S program over the past three years.

Ground‐coupled air waves and diffracted infrasound from the Arequipa earthquake of June 23, 2001

On June 23, 2001, a strong earthquake measuring Mw 8.4 occurred along the coast of south‐central Peru. Coherent infrasonic waves were detected over a period of one hour by the IS08 infrasound station in Bolivia. Analysis of the ground‐coupled air waves shows that the rupture propagated from the northwestern to the southeastern part of the fault with a rupture velocity of 3.3 km/s. The azimuth variation of the infrasonic waves is attributed to a distribution of secondary sources along the highest mountain ranges, which excite infrasonic waves that are diffracted to the ground. The predominant source of infrasound is likely distributed along the Andean Cordillera. Using the azimuth and arrival time determination, the horizontal scale size of the distant source regions of infrasonic waves is reconstructed over distances greater than 400 km.

The Arequipa (Peru) earthquake of June 23, 2001

The Arequipa earthquake of 23 June 2001 hasbeen the largest earthquake (Mw = 8.3)occurredin the last century in southern Peru with amaximum intensity of VIII (MM scale). Focalmechanisms of main shock and three largeraftershocks have been studied, showingthrusting solutions for main shock and twoaftershocks and normal motion for the eventof July, 5. The rupture area has beenobtained from distribution of aftershocks.The occurrence of the Arequipa earthquakeis related with the convergence processbetween the Nazca and South Americaplates.