Recent Great Earthquakes Research Articles

Properties of boiled sand samples from various liquefied ground sites caused by recent great earthquakes in japan and worldwide

Properties of boiled sand samples from various liquefied ground sites caused by recent great earthquakes in japan and worldwide

The impact of erosion on fault segmentation in thrust belts: Insights from thermochronology and fluvial shear stress analysis (southern Longmen Shan, eastern Tibet)

Along the southern Longmen Shan thrust belt in eastern Tibet, the Dayi subsegment stands out as it remained unruptured in both the 2008 Wenchuan and the 2013 Lushan earthquakes. Whether localized weak materials or differential erosion caused this fault segmentation is unclear. According to the critical-taper wedge theory, these two mechanisms would generate distinct morphotectonic features and erosional distributions, such as a recess vs. a salient structure at the range front, and higher vs. lower erosion rate than that of the adjacent areas along strike in the hinterland, respectively. We integrated two independent methods to evaluate these mechanisms. We obtained 10 apatite fission track and two apatite (U-Th)/He dates from the Dayi subsegment, which yield ages of ~3–44 Ma, and deduced an average erosion rate of 0.5–0.6 mm/yr and 0.2–0.4 mm/yr since ~6–8 Ma in the hanging-wall and footwall of the Shuangshi-Dachuan Fault, respectively. We also calculated the fluvial shear stress and erosion rate at 708 sites along five rivers that flow across the faults in the southern Longmen Shan. These two methods yield consistent mean erosion rates, implying an exhumational steady state since at least 5 Ma. Intriguingly, a systematic, heterogeneous pattern of erosion is found on a 3-by-3 grid along and across the Dayi subsegment. In the hinterland, the erosion rate in the Dayi subsegment is lower than that of the adjacent areas along strike, whereas at the range front, the erosion rate in the Dayi subsegment is greater. The spatial patterns of erosion and topography suggest that differential erosion plays a major, but not exclusive, role in regulating the fault segmentation and earthquakes in the Longmen Shan. Moreover, the Dayi subsegment could have acted as a barrier during the recent great earthquakes, posing substantial seismic potential to this region.

Timing and amount of southern Cascadia earthquake subsidence over the past 1700 years at northern Humboldt Bay, California, USA

AbstractStratigraphic, lithologic, foraminiferal, and radiocarbon analyses indicate that at least four abrupt mud-over-peat contacts are recorded across three sites (Jacoby Creek, McDaniel Creek, and Mad River Slough) in northern Humboldt Bay, California, USA (∼44.8°N, −124.2°W). The stratigraphy records subsidence during past megathrust earthquakes at the southern Cascadia subduction zone ∼40 km north of the Mendocino Triple Junction. Maximum and minimum radiocarbon ages on plant macrofossils from above and below laterally extensive (>6 km) contacts suggest regional synchroneity of subsidence. The shallowest contact has radiocarbon ages that are consistent with the most recent great earthquake at Cascadia, which occurred at 250 cal yr B.P. (1700 CE). Using Bchron and OxCal software, we model ages for the three older contacts of ca. 875 cal yr B.P., ca. 1120 cal yr B.P., and ca. 1620 cal yr B.P.For each of the four earthquakes, we analyze foraminifera across representative mud-over-peat contacts selected from McDaniel Creek. Changes in fossil foraminiferal assemblages across all four contacts reveal sudden relative sea-level (RSL) rise (land subsidence) with submergence lasting from decades to centuries. To estimate subsidence during each earthquake, we reconstructed RSL rise across the contacts using the fossil foraminiferal assemblages in a Bayesian transfer function. The coseismic subsidence estimates are 0.85 ± 0.46 m for the 1700 CE earthquake, 0.42 ± 0.37 m for the ca. 875 cal yr B.P. earthquake, 0.79 ± 0.47 m for the ca. 1120 cal yr B.P. earthquake, and ≥0.93 m for the ca. 1620 cal yr B.P. earthquake. The subsidence estimate for the ca. 1620 cal yr B.P. earthquake is a minimum because the pre-subsidence paleoenvironment likely was above the upper limit of foraminiferal habitation. The subsidence estimate for the ca. 875 cal yr B.P. earthquake is less than (<50%) the subsidence estimates for other contacts and suggests that subsidence magnitude varied over the past four earthquake cycles in southern Cascadia.

Repeated occurrence of surface-sediment remobilization along the landward slope of the Japan Trench by great earthquakes

Deep-sea turbidites have been utilized to understand the history of past large earthquakes. Surface-sediment remobilization is considered to be a mechanism for the initiation of earthquake-induced turbidity currents, based on the studies on the event deposits formed by recent great earthquakes, such as the 2011 Tohoku-oki earthquake, although submarine slope failure has been considered to be a major contributor. However, it is still unclear that the surface-sediment remobilization has actually occurred in past great earthquakes. We examined a sediment core recovered from the mid-slope terrace (MST) along the Japan Trench to find evidence of past earthquake-induced surface-sediment remobilization. Coupled radiocarbon dates for turbidite and hemipelagic muds in the core show small age differences (less than a few 100 years) and suggest that initiation of turbidity currents caused by the earthquake-induced surface-sediment remobilization has occurred repeatedly during the last 2300 years. On the other hand, two turbidites among the examined 11 turbidites show relatively large age differences (~ 5000 years) that indicate the occurrence of large sea-floor disturbances such as submarine slope failures. The sedimentological (i.e., of diatomaceous nature and high sedimentation rates) and tectonic (i.e., continuous subsidence and isolated small basins) settings of the MST sedimentary basins provide favorable conditions for the repeated initiation of turbidity currents and for deposition and preservation of fine-grained turbidites. The MST small basin is a suitable site for examining deep-sea turbidite paleoseismology.

Effects of Earthquake Faulting on Civil Engineering Structures

Ground motion characteristics, deformation and surface breaks of earthquakes depend upon the causative faults. Their effects on the seismic design of engineering structures are almost not considered in the present codes of design although there are attempts to include in some countries (i.e. USA, Japan, Taiwan, and Turkey). In this study, the authors first describe ground motions, crustal deformation and surface break observations caused by earthquakes having different faulting mechanism. Then some laboratory experiments were carried out to simulate the motions during normal and thrust faulting and their effects on model structures. And then, the effects of surface ruptures and deformations due to earthquake faulting on the response and stability engineering structures through observations in recent great earthquakes are presented. Finally, some recommendations for the design of structures with the consideration of permanent ground deformation in addition to ground shaking, which may be used in the development of seismic codes incorporating the effect of permanent deformation on structures, are proposed.

The Accumulation of Slip Deficit in Subduction Zones in the Absence of Mechanical Coupling: Implications for the Behavior of Megathrust Earthquakes

AbstractThe distribution of slip during subduction megathrust earthquakes depends on the slip deficit that accumulates on the plate interface prior to the event. We develop 3‐D finite element models of subduction zones to investigate how locked zones restrict surrounding regions on the plate boundary from sliding. What is new is that we quantify the slip around asperities on the megathrust. The models show plate interface slip increasing from zero at the edge of a locked zone to the relative plate motion over a distance of ~200 km along the megathrust. This area of reduced slip accumulates a seismic moment deficit up to 10 times larger than the moment deficit in the asperity alone. Updip of locked areas, slip at the trench can be reduced by more than 50% of the plate motion. Despite large displacements of the upper plate near the trench, this region moves as a semirigid block. Rupture models of the 2011 Tohoku earthquake, its tsunami characteristics, and geophysical observations near the trench can be interpreted to reflect the consequences of slip deficit accumulated on a low friction interface updip of the seismogenic zone. Neighboring asperities affect plate interface slip in a nonlinear way. Multiple asperities have overlapping pseudo‐coupled regions that may restrict the magnitude of coseismic slip in single‐asperity ruptures. Once an earthquake has a rupture length greater than ~250 km, it may recover the entire accumulated slip deficit. This is consistent with the magnitude of coseismic slip in several recent great megathrust earthquakes.

Historical Nankai-Suruga megathrust earthquakes recorded by tsunami and terrestrial mass movement deposits on the Shirasuka coastal lowlands, Shizuoka Prefecture, Japan

Geological investigations of coastal sediment sequences play a key role in verifying earthquake and tsunami characteristics inferred from historical records. In this paper, we present a multi-proxy investigation of a coastal lowland site facing the Nankai-Suruga megathrust and appraise evidence for tsunamis and earthquake-triggered terrestrial mass movements occurring over the last 800 years. Combining a high-resolution chronology with X-ray computed tomography and analyses of particle size, diatoms, pollen, non-pollen palynomorphs and aerial photographs, we present the most compelling geological evidence of the 1361 CE Kōan (also known as Shōhei) tsunami reported to date from any site along the megathrust. This finding is consistent with either of two recent hypotheses: a single larger rupture of both the Nankai and Tōnankai regions or two smaller ruptures separated by a few days. Enhancing the site chronology using Bayesian age modelling, we verify evidence for inundation during the 1498 CE Meiō tsunami. While previous investigations identified evidence for historically recorded tsunamis in 1605, 1707 and 1854 CE and a storm surge in 1680 or 1699 CE, we encountered a thick sand layer rather than discrete extreme wave deposits in this interval. The overprinting of evidence highlights the potential for geological records to underestimate the frequency of these events. A terrestrial mass movement also deposited a sand layer at the site; radionuclide dating and aerial photographs provide independent confirmation that this may have been triggered by intense shaking in 1944 CE during the most recent great Nankai-Suruga megathrust earthquake.

Ongoing deformation of Antarctica following recent Great Earthquakes

AbstractAntarctica's secular motion is thought to be almost everywhere governed by horizontal rigid plate rotation plus three‐dimensional deformations due to past and present changes in ice ocean loading, known as glacial isostatic adjustment (GIA). We use geodetic data to investigate deformation following the 1998 M ~8.2 Antarctic intraplate Earthquake and show sustained three‐dimensional deformation along East Antarctica's coastline, 600 km from the rupture location. Using a model of viscoelastic deformation, we are able to match observed northward velocity changes, and either east or height, but not all three directions simultaneously, apparently partly due to lateral variations in mantle rheology. Our modeling predicts that much of Antarctica may still be deforming, with further deformation possible from the 2004 M 8 Macquarie Ridge Earthquake. This previously unconsidered mode of Antarctic deformation affects geodetic estimates of plate motion and GIA; its viscous nature raises the prospect of further present‐day deformation due to earlier Great Earthquakes.

砂地盤に支持された直接基礎構造物の地震時応答に及ぼす地下水位の影響

It is pointed out that the input acceleration to a building may be small compared with the acceleration of ground surface in the recent great earthquakes. In this paper, dynamic centrifuge tests using a rigid structure supported by saturated sand deposit were performed to investigate the influence of groundwater level. It was shown that the foundation was adsorbed to the ground by negative excess pore water pressure in case of groundwater level equal to the foundation base. Therefore, there is a possibility that the groundwater level has affected the structure damage during severe earthquakes.

Detection of gravity changes before powerful earthquakes in GRACE satellite observations

<p>The variations of gravity field have been analyzed in this article, in order to find disturbances in the vicinity of recent great earthquakes epicenters including Chile (February 27, 2010), Tohoku-Oki (March 11, 2011) and Indian Ocean (April 11, 2012) prior to the events. For this purpose, the 10 years long time series of gravitational gradient components obtained from weekly Gravity Recovery And Climate Experiment (GRACE) solutions have been used. Some of gravitational gradient components are independent to GRACE stripy error and amplify high frequency components of gravity field. Therefore that preseismic activity can be better illustrated. The interquartile method has been used to construct the higher and lower bounds in time series to detect outlying solution outside the bounds associated with impending earthquakes. Afterwards, Nonlinear Auto-Regressive models with eXogenous inputs (NARX) neural network has been proposed in the detection process of prominent gravity field anomalies prior the earthquakes. Both methods detect considerable anomalous occurrences during 2-5 weeks prior to the earthquakes. Our results statistics show that the anomalous deviations before the earthquakes have different signs and amplitudes at different cases.</p>

Crustal earthquake triggering by pre-historic great earthquakes on subduction zone thrusts

Triggering of earthquakes on upper plate faults during and shortly after recent great (M > 8.0) subduction thrust earthquakes raises concerns about earthquake triggering following Cascadia subduction zone earthquakes. Of particular regard to Cascadia was the previously noted, but only qualitatively identified, clustering of M > ~6.5 crustal earthquakes in the Puget Sound region between about 1200–900 cal years B.P. and the possibility that this was triggered by a great Cascadia thrust subduction thrust earthquake, and therefore portends future such clusters. We confirm quantitatively the extraordinary nature of the Puget Sound region crustal earthquake clustering between 1200–900 cal years B.P., at least over the last 16,000. We conclude that this cluster was not triggered by the penultimate, and possibly full-margin, great Cascadia subduction thrust earthquake. However, we also show that the paleoseismic record for Cascadia is consistent with conclusions of our companion study of the global modern record outside Cascadia, that M > 8.6 subduction thrust events have a high probability of triggering at least one or more M > ~6.5 crustal earthquakes.

The Poetry of Diabetes and the Wuhan APACPH Conference

As this issue of the Asia-Pacific Journal of Public Health (APJPH) goes to press, we will be meeting in Wuhan for the 45th Asia Pacific Academic Consortium for Public Health (APACPH) Conference. Wuhan has a 3500-year history of education and scholarship, a tradition that is continued in the modern universities located here. During the eighth century, the Golden Age of the Tang Dynasty, one of China’s greatest classical poets, Li Bai (李白), traveled around the country writing poetry and sampling the local wines. He was born in the far West, probably in present-day Kazakhstan or Kyrgyzstan where his family was in exile from southeast China. At the age of 5 years, his family moved to Jiangyouin Sichuan Province, where he studied the classics and gained skills in Chinese marital arts. There is a statue to his memory in that city, which has survived the recent Great Western China Earthquake. 1 Later during his travels, Li Bai stopped for a period in Wuhan as he travelled along the Yangtze River. He is remembered for naming the city as “River City” (江城). Wuhan is the city’s present name dating from early in the 20th century following several amalgamations. Because of its beautiful location on the mighty river with its lakes and mountains nearby, Wuhan will always be thought of as a beautiful “River City.” One of the best known poems that Li Bai is remembered for is his poem “To the Moon” (静夜思) (which is only 20 words long) and its descriptive of nature while the wandering poet reveals his longing for his home. Seeing the moonlight in front of my bed – I took it for frost on the ground! Lifting my head to watch the bright moon, I thought of hometown when I bent my head The round shape of full moon in Chinese culture has many meanings, including unity, closeness, completeness, healthy, peaceful, and immortality. The moon was seen as a symbol of protection. The image of a full moon rising over the river is also an appropriate one for public health. The circle represents completeness or wholeness, which is the goal of public health. Public health is characterized by scientific assessment and rigorous cost-effectiveness evaluations as we seek to make individuals and populations whole, using the best of a seething river of options made available in our modern world. We could really stretch the analogy and imagine the “hometown” he is referring to his early origins, which is an increasingly important topic in public health. Li Bai wrote more than 1000 poems before he died at the age of 58 and is remembered as one of

Long-Term Oxygen Therapy in Japan: History, Present Status, and Current Problems

Historically, the progress of long term-oxygen therapy (LTOT) in Japan has been characterized by collaboration among academic groups, policy makers, and industrial companies. The public health insurance program has covered the cost of LTOT since 1985. Thomas Petty's group in Denver enthusiastically carried out the public implementation of LTOT and conveyed the concept of pulmonary rehabilitation for the processing with LTOT. Although the target diseases of LTOT in Japan tended to be chronic obstructive pulmonary disease or sequelae of primary lung tuberculosis, it was soon applied for cardiac diseases as well as other pulmonary diseases. Together with increasing medical costs for geriatric patients, the political conversion from hospital based care of a traditional style to home care system has been performed, with two background reasons: the improvement of quality of life of patients and the reduction of the medical expense. Presently, LTOT plays a pivotal role in the successful implementation of home respiratory care for elderly patients. In addition, this promotes comprehensive pulmonary rehabilitation, a team approach, and close liaisons between primary care and hospitals. Currently, the total number of patients using LTOT exceeds 150,000. In Japan, LTOT resulted in an advancement in the medical care as well as in administrative decision to introduce it as a nationwide system after analyzing the results of opinion polls of patients with respiratory failure. However, the recent great earthquake in East Japan revealed that many unresolved problems remain for these patients, and these issues are of great concern.

Analysis of seismic magnitude differentials (m b−M w) across megathrust faults in the vicinity of recent great earthquakes

Spatial variations in underthrusting earthquake seismic magnitude differentials (mb − Mw) are examined for plate boundary megathrusts in the vicinity of the 26 December 2004 Sumatra-Andaman (Mw 9.2), 2010 Maule, Chile (Mw 8.8), and 11 March 2011 Tohoku, Japan (Mw 9.1) great earthquakes. The magnitude differentials, corrected for ω-squared source spectrum dependence on seismic moment, provide a first-order probe of spatial variations of frequency-dependent seismic radiation. This is motivated by observations that the three great earthquakes all have coherent short-period radiation from the down-dip portions of their ruptures as imaged through back-projections, but little coherent short-period energy from shallower regions where large coseismic slip occurred. While there is substantial scatter in the magnitude measures, all three regions display some increase in relative strength of short-period seismic waves with depth, with the pattern being strongest for Sumatra and Japan where the deeper portion of the seismogenic zone is below the overriding crust. Other regions such as the Kuril Islands, Aleutians, Peru, and Southern Sumatra/Sumba show little, if any, depth pattern in the magnitude differentials. Variation in material and frictional properties over particularly wide seismogenic megathrusts likely produce the depth-dependence observed in both mb−Mw residuals and great earthquake seismic radiation.

Coseismic and postseismic stress rotations due to great subduction zone earthquakes

The three largest recent great subduction zone earthquakes (2011 M9.0 Tohoku, Japan; 2010 M8.8 Maule, Chile; and 2004 M9.2 Sumatra‐Andaman) exhibit similar coseismic rotations of the principal stress axes. Prior to each mainshock, the maximum compressive stress axis was shallowly plunging, while immediately after the mainshock, both the maximum and minimum compressive stress axes plunge at ∼45°. Dipping faults can be oriented for either reverse or normal faulting in this post‐mainshock stress field, depending on their dip, explaining the observed normal‐faulting aftershocks without requiring a complete reversal of the stress field. The significant stress rotations imply near‐complete stress drop in the mainshocks, with >80% of the pre‐mainshock stress relieved in the Tohoku and Maule earthquakes and in the northern part of the Sumatra‐Andaman rupture. The southern part of the Sumatra‐Andaman rupture relieved ∼60% of the pre‐mainshock stress. The stress axes rotated back rapidly in the months following the Tohoku and Maule mainshocks, and similarly in the southern part of the Sumatra‐Andaman rupture. A rapid postseismic rotation is possible because the near‐complete stress drop leaves very little “background” stress at the beginning of the postseismic reloading. In contrast, there has been little or no postseismic rotation in the northern part of the Sumatra‐Andaman rupture over the 7 years since the mainshock. All M ≥8.0 subduction earthquakes since 1990 with an adequate number of pre‐ and post‐mainshock events were evaluated, and not all show similar coseismic stress rotations. Deeper earthquakes exhibit smaller coseismic stress rotations, likely due to increasing deviatoric stress with depth.

A Method for Rapid Estimation of Moment Magnitude for Early Tsunami Warning Based on Coastal GPS Networks

The recent great earthquakes of 26 December 2004 (Sumatra, Indonesia, Mw 9.2), 26 February 2010 (Maule, Chile, Mw 8.8), and 11 March 2011 (Tohoku-oki, Japan, Mw 9.0) have once again brought to the forefront the urgent need for early tsunami warning. These warnings mostly rely on magnitude and location of an earthquake. A large/great magnitude subduction-zone earthquake with rupture area extending up to the trench is potentially a tsunamigenic event. The appropriate magnitudes for tsunami warning are those that are based on long-period seismic waves (Abe 1979), e.g. , the moment magnitude, Mw (Kanamori 1977). Recently, W -phase (the long-period wave that arrives between P and S waves) has been used to compute Mw (Kanamori and Rivera 2008; Hayes et al. 2009). This magnitude can be determined in a relatively short time. For example, the first moment tensor solutions of the Tohoku-oki earthquake, based on inversion of W -phase at teleseismic distances, became available in 20 min (Duputel et al. 2011). For this reason, Mw computed from W -phase is especially useful for tsunami alerts at distant sites. It is at local distances that early tsunami warning becomes difficult. Even then, Mw based on inversion of W -phase recorded at regional distances may be useful. Tests show that Mw of Mexican subduction thrust earthquakes, based on W -phase recorded on broadband, regional seismograms, can be estimated in ∼7 min after the occurrence of the event (Perez-Campos et al. 2010). In recent years there has been an increase in GPS stations along the coastal region of some subduction zones. Some of these stations are operated in continuous mode (either in real-time high-rate mode or periodic low-rate download mode), and others in campaign mode. Static displacement vectors obtained from GPS data …

Real‐time inversion of GPS data for finite fault modeling and rapid hazard assessment

Responses to recent great earthquakes and ensuing tsunamis in Sumatra, Chile, and Japan, with the resulting loss of life and damage to infrastructure demonstrate that our ability to ascertain the full extent of slip of catastrophic earthquakes and their tsunamigenic potential in the first minutes after the initiation of rupture is problematic. Regional GPS networks such as those in western North America and Japan are complementary to seismic networks by being able to directly measure displacements close to the source during large earthquakes in real time. We report on rapid modeling of two large earthquakes, the 2003 Mw 8.3 Tokachi‐oki earthquake 100 km offshore Hokkaido Island using 356 GEONET stations and the 2010 Mw 7.2 El Mayor‐Cucapah earthquake in northern Baja California using 95 CRTN stations in southern California about 75 km northwest of the epicenter. Working in a simulated real‐time mode, we invert for finite fault slip in a homogeneous elastic half‐space using Green's functions obtained from Okada's formulation. We compare two approaches: the first starts with a catalog of pre‐defined faults, while the second uses a rapid centroid moment tensor solution to provide an initial estimate of the ruptured fault plane. In either case, we are able to characterize both earthquakes in less than two minutes, reducing the time necessary to obtain finite fault slip and moment magnitude for medium and greater earthquakes compared to traditional methods by an order of magnitude.

Influence of the pre-existing Xiaoyudong salient in surface rupture distribution of the Mw 7.9 Wenchuan earthquake, China

Field investigations show that the Wenchuan earthquake on the 12th of May 2008 ruptured two NW-dipping imbricate reverse faults along the Longmen Shan fault zone. The length of the Beichuan–Yingxiu Fault reaches nearly 240km. Southeast of this fault, a smaller displacement occurred along the Guanxian–Jiangyou Fault, which has a length of about 70km. A NW-striking left-lateral reverse fault, the Xiaoyudong Fault, was clearly observed between these two main surface ruptures. This co-seismic surface rupture pattern is one of the most complicated patterns of recent great earthquakes. In order to clarify how rupture progressed northward during the Wenchuan earthquake, we conducted a detailed investigation including rupture tracing, displacement measurement, fault kinematic estimation, and stress analysis of the Xiaoyudong area. Our results show that the Xiaoyudong Fault is not a simple tear fault. In contrast, it is an independent active fault located on the northern boundary of the Xiaoyudong salient. The Xiaoyudong salient is an independent topographic highland occupying a surface area of approximately 100km2. From a stratigraphic point of view, this highland is a little older than the adjacent area. The s-shape stream north of the Xiaoyudong salient indicates that the Xiaoyudong Fault is still active. The Xiaoyudong salient plays an important role in controlling fault propagation and stress delivery. When the Wenchuan earthquake occurred in the south of the Xiaoyudong salient, this salient partially impeded the northward propagating rupture and dispersed it into two branches to the north. The rupture distribution north of Xiaoyudong would be significantly different without this salient. The existence of the Xiaoyudong salient and the rupture pattern of the Wenchuan earthquake also prove that the multi-segment rupturing model is a better approximation than a single-segment model for estimating the maximum magnitude of the paleo-earthquake of the Longmen Shan fault zone.

Evidence for earthquake triggering of large landslides in coastal Oregon, USA

Landslides are ubiquitous along the Oregon coast. Many are large, deep slides in sedimentary rock and are dormant or active only during the rainy season. Morphology, observed movement rates, and total movement suggest that many are at least several hundreds of years old. The offshore Cascadia subduction zone produces great earthquakes every 300–500years that generate tsunami that inundate the coast within minutes. Many slides and slide-prone areas underlie tsunami evacuation and emergency response routes. We evaluated the likelihood of existing and future large rockslides being triggered by pore-water pressure increase or earthquake-induced ground motion using field observations and modeling of three typical slides. Monitoring for 2–9years indicated that the rockslides reactivate when pore pressures exceed readily identifiable levels. Measurements of total movement and observed movement rates suggest that two of the rockslides are 296–336years old (the third could not be dated). The most recent great Cascadia earthquake was M 9.0 and occurred during January 1700, while regional climatological conditions have been stable for at least the past 600years. Hence, the estimated ages of the slides support earthquake ground motion as their triggering mechanism. Limit-equilibrium slope-stability modeling suggests that increased pore-water pressures could not trigger formation of the observed slides, even when accompanied by progressive strength loss. Modeling suggests that ground accelerations comparable to those recorded at geologically similar sites during the M 9.0, 11 March 2011 Japan Trench subduction-zone earthquake would trigger formation of the rockslides. Displacement modeling following the Newmark approach suggests that the rockslides would move only centimeters upon coseismic formation; however, coseismic reactivation of existing rockslides would involve meters of displacement. Our findings provide better understanding of the dynamic coastal bluff environment and hazards from future subduction-zone earthquakes.

The Short-Term Effect of the Recent Great Earthquake on the General Functioning Status of Psychiatric Patients Near Tokyo

Back to table of contents Previous article Next article Communications and UpdatesFull AccessThe Short-Term Effect of the Recent Great Earthquake on the General Functioning Status of Psychiatric Patients Near TokyoMasanori Saito, M.D.Masanori SaitoSagamihara, JapanSearch for more papers by this author, M.D.Published Online:1 Jun 2011https://doi.org/10.1176/appi.ajp.2011.11030450AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail To the Editor: Kitasato University East Hospital is located about 40 km southwest of Tokyo. During the earthquake on March 11, 2011, the movement around us measured upper 5 on the Japan Meteorological Agency seismic intensity scale. During the first week after the earthquake, I treated 155 psychiatric patients, of whom 141 had regularly consulted me before. These included 120 outpatients (54 with a diagnosis of epilepsy, 32 with schizophrenia, 11 with a mood disorder, eight with an adjustment disorder, five with dementia, and 10 others) and 21 inpatients (two with epilepsy, nine with schizophrenia, four with mood disorder, five with adjustment disorder, and one with dementia). No patients with acute stress disorder came to see me during the first week after the earthquake, and almost all of the patients who did come for treatment expressed their fear of the quake and the aftershocks.Of those 141 regular patients, five (three outpatients and two inpatients) experienced either a marked increase in seizure frequency or a marked decrease in score on the Global Assessment of Functioning Scale (GAF) during that first week. An outpatient with epilepsy was admitted to another hospital for the treatment of status epilepticus that might have been related to aspiration pneumonia after the quake. An inpatient with temporal lobe epilepsy has been experiencing complex partial seizures every time an aftershock occurs, and an inpatient with schizophrenia saw for the first time vivid visual hallucinations of clouds of eels crawling on the floor (the patient's GAF score decreased from 55 to 30). An outpatient with delusional disorder expressed her strong wish to have committed suicide before the terrible quake (her GAF score decreased from 50 to 35), although she did not attempt it. An outpatient with adjustment disorder needed a new prescription (her GAF score decreased from 85 to 60). Interestingly, two outpatients with schizophrenia reported that their sleep-wake cycle had somehow improved after the earthquake. The remaining patients showed no major change in their functional status during the first week after the earthquake.Sagamihara, JapanThe author reports no financial relationships with commercial interests.Accepted for publication in April 2011. FiguresReferencesCited byDetailsCited ByDisaster and Military Medicine, Vol. 1, No. 1Psychiatry and Clinical Neurosciences, Vol. 68, No. 3 Volume 168Issue 6 June 2011Pages 649-649 Metrics PDF download History Accepted 1 April 2011 Published online 1 June 2011 Published in print 1 June 2011