Liquefaction Features Research Articles

Probabilistic methodology for the analysis of paleoliquefaction features

Paleoliquefaction features can be used to estimate lower bounds on the magnitude and ground motion associated with the earthquake that caused the liquefaction feature. The engineering back-analysis of paleoliquefaction features is usually conducted using state of the practice liquefaction-triggering analysis methodologies. Recent studies have shown that these methodologies are associated with variable probabilities of liquefaction depending on the soil parameters. This would imply that estimates of magnitude and ground motion intensity obtained from these methodologies would not be consistent for all soil sites. Moreover, these estimates could be unconservative. In this paper, the use of a probabilistic methodology for the back-analysis of paleoliquefaction features is proposed. The proposed methodology permits the incorporation of model and parameter uncertainty into the analysis and results in more robust estimates of past magnitude and a measure of the uncertainty associated with these predictions. Previously published paleoliquefaction data are used to demonstrate the applicability of the proposed method. Magnitude estimates obtained with the proposed method do not differ significantly from those obtained using deterministic methodologies, but the proposed methodology permits a quantification of the uncertainty associated with magnitude estimates.

Co-seismic secondary surface fractures on southeastward extension of the rupture zone of the 2005 Kashmir earthquake

After the 2005 Kashmir earthquake, we mapped surface ground fractures in Tangdhar, Uri, Rajouri and Punch sectors and liquefaction features in Jammu area lying close to the eastern side of the Line of Control (LOC) in Kashmir, India. The NW trending ground fractures occurred largely in the hanging wall zone of the southeastern extension of the causative fault in Tangdhar and Uri sectors. The principal compressive stress deduced from the earthquake induced ground fractures is oriented at N10°, whereas the causative Balakot–Bagh fault strikes 330°. The fault-plane solution indicates primarily SW thrusting of the causative fault with a component of strike–slip motion. The ground fractures reflect pronounced strike–slip together with some tensile component. The Tangdhar area showing left-lateral strike–slip motion lies on the hanging wall, and the Uri region showing right-lateral strike–slip movement is located towards the southeastern extension of the causative fault zone. The shear fractures are related to static stress that was responsible for the failure of causative fault. The tensile fractures with offsets are attributed to combination of both static and dynamic stresses, and the fractures and openings without offsets owe their origin due to dynamic stress. In Punch–Rajouri and Jammu area, which lies on the footwall, the fractures and liquefactions were generated by dynamic stress. The occurrence of liquefaction features in the out board part of the Himalayan range front near Jammu is suggestive of stress transfer ∼ 230 km southeast of the epicenter. The Balakot–Bagh Fault (BBF), the Muzaffarabad anticline, the rupture zone of causative fault and the zone of aftershocks — all are aligned in a ∼ 25 km wide belt along the NW–SE trending regional Himalayan strike of Kashmir region and lying between the MBT and the Riasi Thrust (Murree Thrust), suggesting a seismogenic zone that may propagate towards the southeast to trigger an earthquake in the eastern part of the Kashmir region.

Synsedimentary deformation of Pleistocene glaciolacustrine deposits in the Albese con Cassano Area (Southern Alps, Northern Italy), and possible implications for paleoseismicity

We describe and interpret the well exposed soft-sediment deformations preserved in a Mid-Pleistocene proglacial sequence outcropping at Albese con Cassano, near Como (Southern Alps, N Italy). The observed deformations affect six distinct stratigraphic intervals within the same depositional sequence. The stratigraphy of this sequence, the geomorphic setting, and the careful geological mapping of the area clearly show that these deformations are not the result of glaciotectonics or cryoturbation, but are due to six separate events of synsedimentary liquefaction. In particular, the 3 basal deformed units include sand and gravel volcanoes that formed at the bottom of a proglacial lake. We examined several hypothesis of possible causative mechanism for the formation of these features. Taking into account all the information available on the local geology and sedimentary environment, it is possible to assess that the liquefaction features at Albese con Cassano had a coseismic origin. To our knowledge, this would be the first report of similar evidence of paleoseismicity in the Lombardia Southern Alps. Also, there is no record of historical liquefaction triggered by seismic events in an area of ca. 70 km of radius near Albese con Cassano, including the town of Como, the large metropolitan area of Milano and most of W Lombardia, that is one of the largest industrial districts in Europe. Therefore, the interpretation of the observed deformations can have critical impact for understanding the current seismicity level in the region, and mitigating the associated risk. In this paper we show that this interpretation is not a simple process. Liquefaction features must be treated with caution in order to derive suitable information for seismic hazard characterization, even if their coseismic origin has been definitely proved. It is necessary to understand the amount of seismic shaking (for instance, in terms of local macroseismic intensity) that can have produced that specific feature at that specific site, the location of the causative seismic event (epicenter and focal depth), and eventually its size (in terms of epicentral intensity and/or earthquake magnitude). In the case of Albese con Cassano, the implications in terms of seismic hazard of the observed possible earthquake paleoliquefactions can only be assessed through the definition of several scenarios, taking into account: a) different thresholds of shaking for triggering the described synsedimentary structures, and b) different seismotectonic frameworks related to the Mid-Pleistocene to Holocene evolution of the S Alps, including seismicity induced by isostatic glacial rebound. We conclude that it is worth checking these scenarios in the field with further paleoseismological research on other possible evidence of past earthquakes. There are no unequivocal sedimentological indicators of paleoseismicity, however, when carefully interpreted within the proper local seismotectonic context and compared with other earthquake-induced features, soft-sediment deformations can offer information of critical value for seismic hazard assessment.

Very Large Earthquakes Centered Southwest of the New Madrid Seismic Zone 5,000-7,000 Years Ago

Earthquake-induced liquefaction features, including large sand blows, occur near Marianna, Arkansas, about 75 km southwest of Memphis, Tennessee, and 80 km south of the southwestern end of the New Madrid seismic zone. The Marianna sand blows formed between 5,000 and 7,000 years ago and predate paleoearthquakes attributed to the New Madrid seismic zone. The Marianna sand blows are similar in size to New Madrid sand blows, suggesting that they too formed as a result of very large earthquakes but were centered near Marianna and outside the New Madrid seismic zone. A large sand blow that formed about 3500 B.C. (5,500 years B.P.) may correlate with smaller sand blows to the northeast and southwest up to 175 km away. A compound sand blow that formed about 4800 B.C. (6,800 years B.P.) may have formed as the result of several very large, closely timed earthquakes. A fault zone associated with the eastern Reelfoot Rift margin seems the most likely source of large Middle Holocene earthquakes because of its great length (∼300 km), history of seismic activity, Late Wisconsin–Early Holocene fault movement in western Tennessee, and structural relationship to the New Madrid fault system. Additional study is needed to verify our initial findings, to identify the earthquake source, and to further define the earthquake potential of the Marianna area. If the eastern Reelfoot Rift margin were confirmed to be the source of Middle Holocene earthquakes near Marianna, seismicity would appear to vary in space and time within the Reelfoot Rift system. This would have important hazard implications for currently aseismic faults of the rift system and possibly of other aulacogens embedded in intraplate regions.

Geophysical surveys of earthquake-induced liquefaction deposits in the New Madrid seismic zone

We explore the effectiveness and limitations of electrical and electromagnetic methods in imaging buried, earthquake-induced liquefaction deposits. Geophysical surveys conducted at liquefaction sites in the New Madrid seismic zone (NMSZ) in the central United States demonstrate that these subsurface-imaging techniques can be useful tools in paleoseismology. Paleoseismological studies of liquefaction features provide one of the few means for estimating recurrence intervals of large earthquakes in the NMSZ, a region with widespread evidence of strong ground shaking but short instrumental record. Noninvasive geophysical methods minimize ground disturbance during these studies, an attribute of particular importance when the studies are conducted at federally protected archaeological sites. Surveys such as those described here can be used to locate buried liquefaction deposits and to site trenches for detailed geologic studies.

Optical dating of liquefaction features to constrain prehistoric earthquakes in Upper Assam, NE India—some preliminary results

Optical dating of liquefied sand structures formed during major earthquakes in Upper Assam, northeast of India, has been carried out to constrain the timing of prehistoric earthquakes in this seismically active region. The bleaching of source material and of the same material during the creation of a liquefaction feature was tested using quartz extracted from 21 samples associated with two different liquefaction structures in Upper Assam. Due to the poor sensitivity of quartz from this region, a sensitisation procedure was used in our SAR protocol to reduce the scatter in optical ages. Various internal consistency tests of the measurement protocol and the excellent reproducibility of the OSL ages indicate that the dose estimates from the quartz are accurate and the optical ages reliable. The preliminary OSL ages indicate that the liquefaction features were formed between 1430 AD and 1630 AD. This study demonstrates that using OSL, ‘direct dating’ of prehistoric earthquakes may be possible, if sand blows from liquefied dykes are preserved.

Liquefaction phenomena associated with historical earthquakes in San Juan and Mendoza Provinces, Argentina

Mendoza and San Juan provinces which represent the most seismically active regions of Argentina have been affected by at least nine destructive earthquakes with magnitudes ⩾6.3 in the period 1861–1997. During these events, earthquake-induced liquefaction processes have caused the most severe damages in properties and fields impacting adversely on regional development and economy. Analysing historical liquefaction data we corroborated the relation between liquefaction phenomenon with sediment grain size and depth of phreatic level. We also noted that even the distance from liquefaction features to epicentres increases with earthquake magnitude, previous empirical relations for distance/magnitude are not enough accurate to predict liquefaction feature distance. Moreover, we suggest that when physical conditions of terrain are suitable, liquefaction phenomenon can occur even at greater distances than those established by empirical manner. In addition, regarding potential risk for this seismically region, the most liquefaction vulnerability areas were established taken into account the historical data and the presence of Holocene–Pleistocene deposits with present higher phreatic level. Our findings are essential for future proper territorial planning and they should be useful for minimize economical losses caused by secondary effects in these seismic regions of Argentina.

Three-Dimensional Imaging of Earthquake-induced Liquefaction Features with Ground Penetrating Radar Near Marianna, Arkansas

Ground penetrating radar (GPR) is a powerful tool used to study earthquake-related features such as sand blows and faults. The study area is near Marianna, Arkansas, and the work involves GPR surveys of large elliptical sand deposits. Our primary goal was to locate feeder dikes of sand blows and to image the contact between sand blows and the buried paleosurface in order to optimize the location of trenches. A secondary goal was to image the sand blows in three dimensions to define their sizes and morphology. Trenching large sand blows is costly and provides a limited view of the overall structure. GPR helps to identify possible locations for the venting dikes and to visualize the subsurface features. It also helps to map the locations in the sand blows of tree stumps that are useful for dating. The surveys imaged sharp contacts in near-surface sediments that were confirmed in trenches to represent boundaries between sand blows and buried soils. One survey in particular showed a sharp discontinuity in the boundary related to a large feeder dike. Because sand thickness was no more than 4 m, a 400 MHz antenna was used. This antenna is designed to provide high-resolution images of the upper 5 m of soil. Data acquisition was along parallel profiles oriented normal to the long axes of the sand deposits at all sites. Data reduction and analysis procedures included removal of direct and ground surface effects, frequency filtration, gain control, profile migration, and three-dimensional visualization. In future work, we plan to refine field procedures and test additional survey configurations to ensure the best results. We will survey additional sites to help with the follow-up trenching and sampling work.

Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya

Paleoseismological investigations, brittle fault analysis, and paleostrain calculations combined with the interpretation of satellite imagery and flood wave modeling were used to investigate the seismic and associated glacial hazard potential in Eastern Lunana, a remote area in NW Bhutan. Seismically induced liquefaction features, cracked pebbles, and a surface rupture of about 6.8 km length constrain the occurrence ofM≥ 6 earthquakes within this high‐altitude periglacial environment, which are the strongest earthquakes ever been reported for the Kingdom of Bhutan. Seismicity occurs along conjugate sets of faults trending NE‐SW to NNW‐SSE by strike‐slip and normal faulting mechanism indicating E‐W extension and N‐S shortening. The strain field for these conjugate sets of active faults is consistent with widespread observations of young E‐W expansion throughout southern Tibet and the north Himalaya. We expect, however, that N‐S trending active strike‐slip faults may even reach much farther to the south, at least into southern Bhutan. Numerous glacial lakes exist in the investigation area, and today more than 100 × 106m3of water are stored in moraine‐dammed and supraglacial lakes which are crosscut by active faults. Strong earthquakes may trigger glacial lake outburst floods, and the impact of such flash floods may be worst 80 km downstream where the valley is broad and densely populated. Consequently, tectonic models of active deformation have to be closely linked with glacial hazard evaluation and require rethinking and modification.

Ground Penetrating Radar imaging of two large sand blow craters related to the 2001 Bhuj earthquake, Kachchh, Western India

The 2001 Bhuj earthquake (Mw 7.7) formed several medium to large sand blow craters due to extensive liquefaction of the sediments comprising the Banni plain and Great Rann of Kachchh. We investigated two large closely spaced sand blow craters of different morphologies using Ground Penetrating Radar (GPR) with a view to understand the subsurface deformation, identify the vents and source of the vented sediments. The study comprises velocity surveys, GPR surveys using 200 MHz antennae along three selected transects that is supplemented by data from two trenches excavated. The GPR was able to provide good data on stratigraphy and deformation up to a depth of 6.5 m with good resolution. The GPR successfully imaged the subsurface characteristics of the craters based on the contrasting lithologies of the host sediments and the sediments emplaced in the craters. The GPR also detected three vertical vents of ∼ 1 m width continuing throughout the profile which are reflected as high amplitude vertical events. We conclude that the large sand blows during the 2001 Bhuj earthquake were produced due to liquefaction of sediments in the subsurface at > 6.5 m depth and that the clay-rich sediments of the Banni plain have behaved as the fine grained cap over it. The present study provides a modern analogue for comparing the liquefaction features of past great earthquakes (for example, the 1819 earthquake) that have occurred in the Kachchh region to understand the phenomena of liquefaction.

未固結〜半固結堆積物中の変形構造形成の解釈

It has long been recognized that unconsolidated or partially consolidated sediments can be intensely deformed during burial, either from gravity-driven subhorizontal extension, or from tectonic shortening. Such deformation can be evaluated in the context of experimental and empirical results from engineering geology literature. We try to summarize this knowledge using several submarine and on-land examples that illustrate the concepts of pore-fluid pressure, shaking, permeability, and consolidation, and are applicable to the interpretation of geologic structures that develop in unconsolidated or partially consolidated sediments. We first review dish, web, and vein structures, scaly clay and liquefaction features, which are typical of unconsolidated or partially consolidated sediments along convergent plate margins. Then, some experimental aspects of permeability test results are applied to fluid flow phenomena in and around accretionary prisms to characterize the role and the importance of fluid flow parallel to the σ2 direction. The results are further applied to explain the concentration of hot springs of a non-volcanic origin along active, strike-slip faults, as well as how seepage along convergent margins occurs in an en echelon pattern on conjugate sets of strike slip faults. Additional experimental work is suggested to develop a better understanding of these geologic structures.

Recording-based identification of site liquefaction

Reconnaissance reports and pertinent research on seismic hazards show that liquefaction is one of the key sources of damage to geotechnical and structural engineering systems. Therefore, identifying site liquefaction conditions plays an important role in seismic hazard mitigation. One of the widely used approaches for detecting liquefaction is based on the time-frequency analysis of ground motion recordings, in which short-time Fourier transform is typically used. It is known that recordings at a site with liquefaction are the result of nonlinear responses of seismic waves propagating in the liquefied layers underneath the site. Moreover, Fourier transform is not effective in characterizing such dynamic features as time-dependent frequency of the recordings rooted in nonlinear responses. Therefore, the aforementioned approach may not be intrinsically effective in detecting liquefaction. An alternative to the Fourier-based approach is presented in this study, which proposes time-frequency analysis of earthquake ground motion recordings with the aid of the Hilbert-Huang transform (HHT), and offers justification for the HHT in addressing the liquefaction features shown in the recordings. The paper then defines the predominant instantaneous frequency (PIF) and introduces the PIF-related motion features to identify liquefaction conditions at a given site. Analysis of 29 recorded data sets at different site conditions shows that the proposed approach is effective in detecting site liquefaction in comparison with other methods.

Late Pleistocene and Holocene paleoseismology of an intraplate seismic zone in a large alluvial valley, the New Madrid seismic zone, Central USA

Late Pleistocene and Holocene paleoseismology of an intraplate seismic zone in a large alluvial valley, the New Madrid seismic zone, Central USA

Spatial and Temporal Characteristics of Paleoseismic Features in the Southern Terminus of the New Madrid Seismic Zone in Eastern Arkansas

Other| July 01, 2005 Spatial and Temporal Characteristics of Paleoseismic Features in the Southern Terminus of the New Madrid Seismic Zone in Eastern Arkansas Haydar J. Al-Shukri; Haydar J. Al-Shukri Department of Applied Science University of Arkansas 2801 S. University Avenue Little Rock, AR 72204 alshukri@seismo.ualr.edu (H.J.A.-S.) Search for other works by this author on: GSW Google Scholar Robert E. Lemmer; Robert E. Lemmer Leighton and Associates, Inc. Irvine, CA (R.E.L.) Search for other works by this author on: GSW Google Scholar Hanan H. Mahdi; Hanan H. Mahdi Department of Applied Science University of Arkansas 2801 S. University Avenue Little Rock, AR 72204 alshukri@seismo.ualr.edu (H.H.M., J.B.C.) Search for other works by this author on: GSW Google Scholar Jeffrey B. Connelly Jeffrey B. Connelly Department of Applied Science University of Arkansas 2801 S. University Avenue Little Rock, AR 72204 alshukri@seismo.ualr.edu (H.H.M., J.B.C.) Search for other works by this author on: GSW Google Scholar Author and Article Information Haydar J. Al-Shukri Department of Applied Science University of Arkansas 2801 S. University Avenue Little Rock, AR 72204 alshukri@seismo.ualr.edu (H.J.A.-S.) Robert E. Lemmer Leighton and Associates, Inc. Irvine, CA (R.E.L.) Hanan H. Mahdi Department of Applied Science University of Arkansas 2801 S. University Avenue Little Rock, AR 72204 alshukri@seismo.ualr.edu (H.H.M., J.B.C.) Jeffrey B. Connelly Department of Applied Science University of Arkansas 2801 S. University Avenue Little Rock, AR 72204 alshukri@seismo.ualr.edu (H.H.M., J.B.C.) Publisher: Seismological Society of America First Online: 09 Mar 2017 Online ISSN: 1938-2057 Print ISSN: 0895-0695 © 2005 by the Seismological Society of America Seismological Research Letters (2005) 76 (4): 502–511. https://doi.org/10.1785/gssrl.76.4.502 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Haydar J. Al-Shukri, Robert E. Lemmer, Hanan H. Mahdi, Jeffrey B. Connelly; Spatial and Temporal Characteristics of Paleoseismic Features in the Southern Terminus of the New Madrid Seismic Zone in Eastern Arkansas. Seismological Research Letters 2005;; 76 (4): 502–511. doi: https://doi.org/10.1785/gssrl.76.4.502 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search Abstract The focus of this study is to identify and characterize specific features related to historic or prehistoric earthquakes south of the southern terminus of the New Madrid seismic zone in eastern Arkansas. Aerial photography, field surveys, and trenching reveal the existence of several liquefaction features (sand blows) and linear structures as far as south of Marianna, Arkansas. This is more than 100 km from the currently active segments of the New Madrid seismic zone. Radiocarbon dating indicts that the event(s) that generated some of these features took place about 5500 years B.P. The discovered liquefaction features are significant because they are at a considerable distance from present-day earthquake activity. The implication of this is that they either represent a new earthquake source not previously recognized or that they are related to an earthquake(s) of very large magnitude in the source region of the New Madrid seismic zone. These liquefaction features have very large dimensions (∼110 by 60 m), resembling features in the immediate vicinity of the New Madrid seismic zone, implying that regardless of where the source region was, the ground shaking had to be severe in order to generate them. Detailed investigation of these features may have important implications for earthquake risk mapping in the central United States, as they may provide important constraints on the southern terminus of the New Madrid seismic zone and the magnitude of the characteristic earthquake in the region. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Paleoseismic features as indicators of earthquake hazards in North Coastal, San Diego County, California, USA

New road cut and mass-grading excavations in the north coastal area of San Diego County, California expose heretofore generally unrecognized, probable late Holocene tsunami deposits and paleoseismically deformed sediments. Remnant tsunami deposits occur up to 100 + m in elevation around the margins of modern coastal lagoons and estuaries and, combined with local mima mounds of possible sand blow origin, provide indirect but compelling evidence for the late Quaternary activity of onshore and offshore faults in the immediate study area. Probable paleoliquefaction features are regionally widespread and range from fissures filled with sediments derived from overlying marine terrace sand and soil, to the more traditional sand-filled injection dikes and sills, lateral spreads, and filled craterlets. The source of most liquefied sediment is underlying Tertiary “bedrock sand” and local, Quaternary marine-terrace deposits. A paleoseismic liquefaction origin rather than soft-sediment loading is deduced for these features based on morphology, internal stratigraphy, field setting, and near proximity to known seismogenic sources. Some paleoseismic events impacted late Holocene Indian middens and burial sites. The last seismic event probably occurred within the past 1 to 3 ka, and possibly even records the historic earthquakes of either November 22, 1800 or May 27, 1862. The liquefaction features also affect marine terrace sediments tens of meters above modern regional water levels, inferentially “recording” paleoseismic events in this Mediterranean-type climatic region during winter rains when high-level, perched water saturates the several meter thick source sediments. Based on their regional extent, the paleoseismic features were likely caused by M ∼ 7+ tectonic events inferentially generated by the nearby offshore Newport–Inglewood/Rose Canyon fault system, or possibly by smaller, recently exposed, related and localized faults. Accordingly, the seismic hazard of the north coastal area of San Diego County may be substantially higher than previously assumed, and hence of concern owing to the rapid ongoing and projected population increase.

Soil liquefaction during the Arequipa Mw 8.4, June 23, 2001 earthquake, southern coastal Peru

The Arequipa June 23, 2001, earthquake with a moment magnitude of Mw 8.4 struck southern Peru, northern Chile and western Bolivia. This shallow (29 km deep) interplate event, occurring in the coupled zone of the Nazca subduction next to the southeast of the subducting Nazca ridge, triggered very localized but widely outspread soil liquefaction. Although sand blows and lateral spreading of river banks and road bridge abutments were observed 390 km away from the epicenter in the southeast direction (nearing the town of Tacna, close to the Chile border), liquefaction features were only observed in major river valleys and delta and coastal plains in the meizoseismal area. This was strongly controlled by the aridity along the coastal strip of Southern Peru. From the sand blow distribution along the coastal area, a first relationship of isolated sand blow diameter versus epicentral distance for a single event is ever proposed. The most significant outcome from this liquefaction field reconnaissance is that energy propagation during the main June 23, 2001, event is further supported by the distribution and size of the isolated sand blows in the meizoseismal area. The sand blows are larger to the southeast of the epicenter than its northwestern equivalents. This can be stated in other words as well. The area affected by liquefaction to the northwest is less spread out than to the southeast. Implications of these results in future paleoliquefaction investigations for earthquake magnitude and epicentral determinations are extremely important. In cases of highly asymmetrical distribution of liquefaction features such as this one, where rupture propagation tends to be mono-directional, it can be reliably determined an epicentral distance (between earthquake and liquefaction evidence) and an earthquake magnitude only if the largest sand blow is found. Therefore, magnitude estimation using this uneven liquefaction occurrence will surely lead to underrating if only the shortest side of the meizoseismal area is unluckily studied, which can eventually be the only part exhibiting liquefaction evidence, depending on the earthquake location and the distribution of liquefaction-prone environments.

Evidence for New Madrid Earthquakes in A.D. 300 and 2350 B.C.

Six episodes of earthquake-induced liquefaction are associated with soil horizons containing artifacts of the Late Archaic (3000-500 B.C.) and Early to Middle Woodland (500 B.C.-A.D. 400) cultural periods at the Burkett archaeological site in the northern part of the New Madrid seismic zone, where little information about prehistoric earthquakes has been available. Radiocarbon dating of organic material and analysis of artifacts are used to estimate the ages of the liquefaction features and times of the causative earthquakes. The most recent episode of liquefaction occurred after A.D. 1670, produced small sand dikes, and is probably related to the 1895 Charleston, Missouri earthquake. The preceding episode struck the area in A.D. 300 ± 200 years and generated a sand blow that contains Late Woodland artifacts and buries an Early to Middle Woodland cultural horizon. Four older episodes of liquefaction occurred in 2350 B.C. ± 200 years and may have been produced by a sequence of closely timed earthquakes. The four earlier episodes produced graben structures, sand dikes, and associated sand blows on which a cultural mound was constructed. The Burkett liquefaction features that formed about 2350 B.C. and A.D. 300 are relatively large and similar in age to other liquefaction features in northeastern Arkansas and southeastern Missouri, respectively. If the prehistoric features at the Burkett site and those of similar age elsewhere in the region are the result of the same earthquakes, then this suggests that they were similar in size to the three largest (M 7-8) 1811-1812 New Madrid earthquakes. A New Madrid-type earthquake in A.D. 300 ± 200 years would support an average recurrence time of 500 years. Although this study extends the earthquake chronology back to 2500 B.C., it is uncertain that the record of New Madrid events is complete for the period between 2350 B.C. and A.D. 300. As demonstrated by this study, information about other prehistoric earthquakes may be buried beneath fluvial deposits of the Mississippi River Valley.

Revised Magnitude-bound Relation for the Wabash Valley Seismic Zone of the Central United States

Seismic hazard assessment in the central United States, and in particular the Wabash Valley seismic zone of Indiana-Illinois, frequently relies on empirical estimates of paleoearthquake magnitudes ( M ). In large part these estimates have been made using the magnitude-bound method. Existing region-specific magnitude-bound relations rely heavily on only a few historical earthquakes in the central United States and eastern Canada that induced reported liquefaction features. Recent seismological studies have suggested smaller magnitudes than previously presumed for some of these earthquakes, however, and other studies have reinterpreted site-to-source distances to liquefaction features associated with some of these earthquakes. In this paper, we re-examine historical earthquakes ( M > ∼5) that occurred in the central and eastern United States and eastern Canada; some of these earthquakes triggered liquefaction and others did not. Based on our findings, we reinterpret the region-specific magnitude-bound relation for the Wabash Valley. Using this revised magnitude-bound relation, we present magnitude estimates for four prehistoric earthquakes that occurred in the Wabash Valley seismic zone during Holocene time.

Investigation of Microearthquakes, Macroseismic Data, and Liquefaction Associated with the 1867 Wamego Earthquake in Eastern Kansas

Historical felt earthquakes and instrumentally recorded microseismicity in eastern Kansas and western Missouri have been attributed to the movement of the Nemaha Ridge and Humboldt fault zone (nrhf). Our investigations of the nrhf have concentrated on relocation of microearthquakes in the Kansas catalog, re-evaluation of the 1867 earthquake felt reports, and field studies to determine the presence or absence of sedimentary evidence of earthquake-induced liquefaction. Microearthquakes in the Kansas catalog have been relocated in a joint inversion with 3D seismic velocity variations. This improved set of hypocenters affirms the loose association of seismicity with the basement nrhf structure, even though seismicity does not seem to follow a single, well-defined fault feature. Overall, the association of microearthquakes with the nrhf suggests that it remains a potential source of large earthquakes. Our field investigations confirm that sedimentary deposits with moderate liquefaction susceptibility are present in the vicinity of Wamego and Wabaunsee, Kansas. Soft-sediment deformation features, including flame and dish structures, are present in the late Holocene floodplain deposits of the Kansas River. These features may have formed by liquefaction or by processes unrelated to seismic activity, such as sediment dewatering. We found several clastic dikes that may be attributed to seismically induced liquefaction. Our initial results suggest that liquefaction features are present but may not be pervasive in this region. These data imply that the 5.2 magnitude of the 1867 Wamego earthquake may characterize the seismic source in this location. However, additional field investigations are still necessary to complete the assessment for liquefaction features.

Paleoliquefaction features on Tenerife (Canary Islands) in Holocene sand deposits

On Tenerife, one of the Canary Islands, a series of clastic dikes and tubular vents is attributed to liquefaction of sediments during a high-intensity paleoearthquake. Geotechnical, geological, tectonic, and mineralogical investigations have been carried out to identify the soil composition and structure, as well as the geological processes operating in the area. Geochronological analysis has indicated an age ranging from 10,081±933 to 3490±473 years BP for the liquefaction features. The area in which these liquefaction features are found has undergone tectonic uplift and is affected by two faults. One of these faults was responsible for displacing the Holocene materials. The paleoearthquake responsible for this liquefaction has been analysed in terms of its peak ground acceleration (pga) and magnitude by back calculation analysis based on the cyclic stress and Ishihara methods. A range of 0.22–0.35 g was obtained for the pga, with the value of 0.30 g being selected as most representative. From this, an earthquake-modified Mercalli intensity of I MM=IX was estimated for the liquefaction site. The magnitude-bound method and energy-based approaches were used to determine the magnitude of the paleoearthquake, providing a moment magnitude M in the range of 6.4–7.2; M =6.8 is taken as the representative figure.