Paleoliquefaction Studies Research Articles

Probabilistic seismic source location and magnitude via inverse analysis of paleoliquefaction evidence

In regions of infrequent moderate-to-large earthquakes, historic earthquake catalogs are often insufficient to provide inputs to seismic-hazard analyses (i.e. fault locations and magnitude–frequency relations) or to inform ground-motion predictions for certain seismic sources. In these regions, analysis of relic coseismic evidence, such as paleoliquefaction, is commonly used to infer information about the seismic hazard. However, while paleoliquefaction studies have been performed widely, all existing analysis techniques require a priori assumptions about the causative earthquake’s location (i.e. rupture magnitude and ground motions can otherwise not be estimated). This may lead to inaccurate assumptions in some settings, and by corollary, erroneous results. Accordingly, this article proposes an inversion framework to probabilistically constrain seismic-source parameters from paleoliquefaction. Analyzing evidence at regional scale leads to (a) a geospatial likelihood surface that constrains the rupture location and (b) a probability distribution of the rupture magnitude, wherein source-location uncertainty is explicitly considered. Simulated paleoliquefaction studies are performed on earthquakes with known parameters. These examples demonstrate the framework’s potential, even in cases of limited field evidence, as well as important caveats and lessons for forward use. The proposed framework has the potential to provide new insights in enigmatic seismic zones worldwide.

Late Holocene Deformation near the Southern Limits of the Wabash Valley Seismic Zone of Kentucky and Indiana, Central United States, with Seismic Implications

ABSTRACTThe Wabash Valley seismic zone (WVSZ) is a region of diffuse, modern intraplate seismicity in the central United States with a history of strong, late Quaternary and Holocene seismicity as determined through paleoliquefaction studies. Yet, there are no specific faults linked to these strong WVSZ paleoearthquakes, some of which were as large as Mw 7.2–7.5. A multidisciplinary investigation of a linear, 5-kilometer-long and ∼3-meter-high scarp on the Ohio River floodplain in the southernmost WVSZ in western Kentucky evaluated whether the scarp is a fluvial landform or a tectonic feature. Geomorphic mapping and optically stimulated luminescence geochronology show that the age and orientation of the scarp are inconsistent with surrounding fluvial landforms. Trenching, core drilling, seismic reflection, electrical resistivity profiling, and cross sections of petroleum well logs all indicate a blind fault directly underlies the scarp. The scarp is interpreted to be the fold axis of a down-to-the-west monocline formed in alluvium by slip on the underlying blind fault, herein named the Uniontown fault. The Uniontown fault connects the Hovey Lake fault, striking N20°E and having ∼0.5 km of documented strike-slip offset, with an unnamed fault complex to the south that strikes N40°E, suggesting the Uniontown fault is part of a larger, Paleozoic structure that has been reactivated with strike-slip deformation. Geomorphic mapping utilizing luminescence and radiocarbon geochronology indicates that folding and faulting occurred ∼3.5 ka. Paleoliquefaction was suppressed by a thick clay cap in the main Ohio Valley, but paleoliquefaction features are widespread on Ohio River tributaries. Gravel dikes at one site had a maximum age of 3.4±0.4 ka, confirming the region has experienced strong, late Holocene shaking. Estimates using vertical displacement and rupture length indicate that slip on the Uniontown scarp could produce an Mw 6.2–7.7 earthquake, which is comparable to other large paleoearthquakes in the WVSZ paleoseismic record.

Characterization and Liquefaction Hazard Assessment of Two Hungarian Liquefied Sites from the 1956 Dunaharaszti Earthquake

The seismicity of Hungary can be considered moderately active, nevertheless contemporary reports from the past approx. 350 years documented surface manifestations of liquefaction occurrences. The last such earthquake was the 1956 Dunaharaszti ground motion, for which the location of two liquefied sites could be identified approx. 60 years after the event. This provided an excellent opportunity to analyze possibly the only accessible liquefied sites in Hungary. Analysis of the two sites included field and laboratory tests allowing the back-calculation of maximum horizontal ground acceleration of the earthquake. This parameter was previously unknown because the closest seismometer saturated during the event. The performed back-analysis using the principles of paleoliquefaction studies was the first of such analyses in the country. In areas with low to moderate seismicity, geotechnical engineers often neglect and overlook liquefaction hazard, however, when it is addressed, the hazard is often overestimated due to improper characterization of the seismic loading and site characterization. To explore this observation more deeply, probabilistic seismic and liquefaction hazard assessment were carried out at the two liquefied sites and it was found that this conclusion is also valid for Hungary, but the degree of conservatism of the pseudo-probabilistic procedures decreases with increasing earthquake return period (lower annual probability of occurrence).

Effects of Earthquakes on Flood Hazards: A Case Study From Christchurch, New Zealand

Earthquakes can influence flood hazards by altering the flux, volumes, and distributions of surface and/or subsurface waters and causing physical changes to natural and engineered environments (e.g., elevation, topographic relief, permeability) that affect surface and subsurface hydrologic regimes. This paper analyzes how earthquakes increased flood hazards in Christchurch, New Zealand, using empirical observations and seismological data. Between 4 September 2010 and 4 December 2017, this region hosted one moment magnitude (Mw) 7.1 earthquake, 3 earthquakes with Mw ≥ 6, and 31 earthquakes with local magnitude (ML) ≥ 5. Flooding related to liquefaction-induced groundwater pore-water fluid pressure perturbations and groundwater expulsion occurred in at least six earthquakes. Flooding related to shaking-induced ground deformations (e.g., subsidence) occurred in at least four earthquakes. Flooding related to tectonic deformations of the land surface (fault surface rupture and/or folding) occurred in at least two earthquakes. At least eight earthquakes caused damage to surface (e.g., buildings, bridges, roads) and subsurface (e.g., pipelines) infrastructure in areas of liquefaction and/or flooding. Severe liquefaction and associated groundwater-expulsion flooding in vulnerable sediments occurred at peak ground accelerations as low as 0.15 to 0.18 g (proportion of gravity). Expected return times of liquefaction-induced flooding in vulnerable sediments were estimated to be 100 to 500 years using the Christchurch seismic hazard curve, which is consistent with emerging evidence from paleo-liquefaction studies. Liquefaction-induced subsidence of 100 to 250 mm was estimated for 100-year peak ground acceleration return periods in parts of Christchurch.

The Stratigraphy of Compound Sand Blows at Sites of Recurrent Liquefaction: Implications for Paleoseismicity Studies

Paleoliquefaction studies provide valuable information for seismic hazard analyses in areas where the return period of moderate to large events is longer than the duration of the historical earthquake catalog (e.g., Central-Eastern and Pacific Northwest United States). Toward this end, paleoliquefaction studies require accurate and detailed assessments of individual features and of the extent of the paleoliquefaction field for the event, with the difficulty of accurately interpreting field observations increasing in areas where recurrent liquefaction was triggered by spatiotemporally clustered paleo events. Accordingly, undisturbed features formed by recurrent liquefaction during the 2010–2011 Canterbury, New Zealand, earthquake sequence were studied to facilitate interpretation of paleoliquefaction analogs. Silt drapes demarcated multiple episodes of liquefaction in the sand blows, with the thickness of the silt drapes correlating to the fines content of the liquefied source stratum. However, no ubiquitous trends in the spatial sorting of grain sizes in the coarser fraction of the ejecta underlying silt drapes were observed. This study provides a modern analog to recurrent paleoliquefaction evidence and has important implications for interpretation of seismic hazards.

Paleoliquefaction Studies and the Evaluation of Seismic Hazard

Recent and historical studies of earthquake-induced liquefaction, as well as paleoliquefaction studies, demonstrate the potential usefulness of liquefaction data in the assessment of the earthquake potential of seismic sources. Paleoliquefaction studies, along with other paleoseismology studies, supplement historical and instrumental seismicity and provide information about the long-term behavior of earthquake sources. Paleoliquefaction studies focus on soft-sediment deformation features, including sand blows and sand dikes, which result from strong ground shaking. Most paleoliquefaction studies have been conducted in intraplate geologic settings, but a few such studies have been carried out in interplate settings. Paleoliquefaction studies provide information about timing, location, magnitude, and recurrence of large paleoearthquakes, particularly those with moment magnitude, M, greater than 6 during the past 50,000 years. This review paper presents background information on earthquake-induced liquefaction and resulting soft-sediment deformation features that may be preserved in the geologic record, best practices used in paleoliquefaction studies, and application of paleoliquefaction data in earthquake source characterization. The paper concludes with two examples of regional paleoliquefaction studies—in the Charleston seismic zone and the New Madrid seismic zone in the southeastern and central United States, respectively—which contributed to seismic source models used in earthquake hazard assessment.

Controls on patterns of liquefaction in a coastal dune environment, Christchurch, New Zealand

Liquefaction features in the geological record are important off-fault markers of moderate to large (>5 Mw) paleoearthquakes. The study of contemporary liquefaction features provides a better understanding of where to find past (paleo) liquefaction features which, if correctly identified and dated, can provide information on the occurrence, magnitude and timing of past earthquakes. This is particularly important in areas with blind active faults. This paper describes liquefaction features in the coastal setting of Christchurch (South Island of New Zealand), and explores the role of liquefaction and fluidization in the surface soil profile and their role in controlling surface ejection. The paper also compares the styles of liquefaction surface manifestation in the alluvial and coastal settings, and the role played by the sedimentary architecture in both environments. This analysis contributes to our understanding of which of the two environments provides a better target for paleoliquefaction studies, and which geomorphic setting within those environments is most likely to host paleoliquefaction features. The coastal setting (in particular, young coastal areas, <300 years old) is especially prone to liquefaction because near surface soils are dominated by well-sorted sandy aeolian deposits and a shallow water table exists. Fluidization within the near surface sandy layer that liquefied and in horizons above, due to upward moving pore water, resulted in a very disrupted soil stratigraphy, making it difficult to identify paleoliquefaction features. Therefore, young coastal areas are not the best target for identifying individual paleoliquefaction events. In comparison, the alluvial setting is characterized by sandy point-bar and channel deposits capped by cohesive overbank and abandoned-channel deposits. As a consequence, sand dikes that form in the alluvial settings are well defined, with preservation of the original soil stratigraphy and distinct cross cutting relationships. These conditions make the alluvial setting, along with older coastal deposits (>1000 years old), a better target for paleoliquefaction studies.

Liquefaction Induced during the 2010–2011 Canterbury, New Zealand, Earthquake Sequence and Lessons Learned for the Study of Paleoliquefaction Features

ABSTRACT Very large to moderate earthquakes in the 2010–2011 Canterbury sequence induced liquefaction in parts of Christchurch city and the surrounding region on the South Island of New Zealand. Detailed information gathered about this case of recurrent liquefaction offers important lessons for the study of paleoliquefaction features and the paleoearthquakes that caused them. The Canterbury case demonstrates that liquefaction features are important indicators of strong ground shaking in regions where fault ruptures do not necessarily propagate to the surface, may be masked by later sedimentation, or are otherwise difficult to recognize. Comparison of the liquefaction fields produced by the 2010 M 7.1 Darfield and 2011 M 6.2 Christchurch earthquakes in the Canterbury sequence highlights the influence of site conditions on the geographical distribution of liquefaction features and underscores the need to consider liquefaction susceptibility of sediment and depth of the water table when using paleoliquefaction features to interpret the source area and magnitude of paleoearthquakes. The epicentral distance and size of liquefaction features that formed during the Darfield and Christchurch earthquakes corroborate and further constrain empirical relations used to estimate source areas and magnitudes of paleoearthquakes. Formation of compound sand blows, composed of multiple sand–silt couplets resulting from repeated liquefaction during the Canterbury earthquakes, supports previous interpretations of compound sand blows in the central and western United States. In addition, paleoliquefaction features found in excavations of sand blows that formed during the 2010–2011 Canterbury earthquakes indicate that sites of modern liquefaction are prime targets for paleoliquefaction studies. The depositional environments where liquefaction features form and are preserved help to guide searches for paleoliquefaction features. Information from many sites across a region is needed to develop a chronology of past liquefaction events, to define their liquefaction fields, and to estimate the source areas and magnitudes of paleoearthquakes.

Paleoliquefaction in Christchurch, New Zealand

Liquefaction during the 2010 moment magnitude (Mw) 7.1 Darfield earthquake and large aftershocks (known as the Canterbury earthquake sequence) caused severe damage to land and infrastructure in Christchurch, New Zealand. Liquefaction occurred at Mw-weighted peak ground accelerations (PGA7.5) as low as 0.06 g at highly susceptible sites. Trenching investigations conducted at two sites in eastern Christchurch enabled documentation of the geologic expressions of recurrent liquefaction and determination of whether evidence of pre–Canterbury earthquake sequence liquefaction is present. Excavation to water table depths (∼1–2 m below surface) across sand blow vents and fissures revealed multiple generations of Canterbury earthquake sequence liquefaction “feeder” dikes that crosscut Holocene-to-recent fluvial and anthropogenic stratigraphy. Canterbury earthquake sequence dikes crosscut and intrude oxidized and weathered dikes and sills at both sites that are interpreted as evidence of pre–Canterbury earthquake sequence liquefaction. Crosscutting relationships combined with 14C dating constrain the timing of the pre–Canterbury earthquake sequence liquefaction to post–A.D. 1660 to pre–ca. A.D. 1905 at one site, and post–A.D. 1415 to pre–ca. A.D. 1910 at another site. The PGA7.5 of five well-documented historical earthquakes that caused regional damage between 1869 and 1922 are approximated for the study sites using a New Zealand specific ground motion prediction equation. Only the June 1869 Mw ∼4.8 Christchurch earthquake produces a median modeled PGA7.5 that exceeds the PGA7.5 0.06 g threshold for liquefaction. Prehistoric earthquakes sourced from regional faults, including the 1717 Alpine fault Mw ∼7.9 ± 0.3 and ca. 500–600 yr B.P. Mw ≥ 7.1 Porters Pass fault earthquakes, provide additional potential paleoseismic sources for pre–Canterbury earthquake sequence liquefaction. The recognition of pre–Canterbury earthquake sequence liquefaction in late Holocene sediments is consistent with hazard model-based predicted return times of PGAs exceeding the liquefaction triggering threshold in Christchurch. Residential development in eastern Christchurch from ca. 1860 to 2005 occurred in areas where geologic evidence for pre–Canterbury earthquake sequence liquefaction was present, highlighting the potential of paleoliquefaction studies to predict locations of future liquefaction and to contribute to seismic hazard assessments and land-use planning.

Seismic hazard in Takamatsu Japan from fault trenching and paleo-liquefaction studies

Takamatsu is a harbor city of 330,000 people on the northern shore of Shikoku Island, southwest Japan. Earthquakes in the Nankai Trough, typically of magnitude M 8+, have been considered the primary source of seismic hazard for the island and Takamatsu. A major active fault system, the Median Tectonic Line, runs across the Shikoku from east to west near the north shore. There is no documented historical seismicity associated with this major fault system in Shikoku or with associated faults such as the 20 km Nagao Fault near Takamatsu. Therefore the trenches were cut across some of the more important faults to expose the record of past seismicity. Additional data on past seismicity is derived from paleo-liquefaction studies in the Takamatsu plain. This paper describes the trenching and paleo-seismic studies and discusses the implications of the findings for seismic hazard in Takamatsu.

Identification of liquefaction and deformation features using ground penetrating radar in the New Madrid seismic zone, USA

Ground penetrating radar (GPR) surveys were conducted in the New Madrid seismic zone in the central US. The targets of the GPR surveys were the near-surface sedimentary features associated with seismically induced liquefaction and stratigraphic disturbances. Correlation of the features shown by the GPR data and “ground truth” revealed by geological excavation holds the promise of using GPR to assist optimal selection of future trenching sites. The present paper reports GPR survey results using a 400 MHz antenna at the site of Haynes Farm in Arkansas for paleoliquefaction studies; and using 400 and 100 MHz antennas at three sites along the western scarp of the Sikeston Ridge in Missouri for near-surface deformation studies. The 400 MHz data at the paleoliquefaction site in Haynes Farm characterized an elongated sand blow feature at a depth of about 1 m, with an almost east–west striking orientation. At the Sikeston Ridge site, GPR surveys were carried out at one excavation site near Davis Cemetery in the village of Kewanee, Missouri, using the 400 MHz antenna. Another three GPR profiles with lengths of more than 100 m and crossing the western scarp of the Sikeston Ridge were collected using the 100 MHz antenna. Since the soils in this area are rather sandy, the 100 MHz antenna produced the best data and penetrated to depths of 6–7 m. The GPR surveys reveal similar subsurface deformation features at depth for all three 100 MHz profiles. Correlating GPR profiles with trenching, drilling, and satellite imaging confirms that the stratigraphic disturbances shown at shallow depths are associated with erosional trimming, colluvial deposition, and channel incision of the west margin of the Sikeston Ridge, occurring in the latest Wisconsin time about 10 000 years BP. The examples show that GPR is useful in locating subsurface features in the New Madrid seismic zone for seismic hazard assessments.

The use of liquefaction features in paleoseismology: Lessons learned in the New Madrid seismic zone, central United States

A recent study in the New Madrid seismic zone demonstrates that large uncertainties, often involved but rarely expressed, in paleoliquefaction studies can be reduced by conducting detailed investigations at the most promising sites for dating liquefaction features. During the site investigations, care must be taken to collect samples that will provide close maximum and minimum dates for liquefaction features. It is advisable to use two-sigma calibrated dates, rather than one-sigma calibrated dates or radiocarbon ages, when estimating ages of liquefaction features. Well-constrained ages of individual liquefaction features should provide the basis for estimating the timing of paleoearthquakes and correlating features across a region. As uncertainty in ages of liquefaction features decreases, confidence in estimates of timing, source areas and magnitudes of paleoearthquakes increases. The New Madrid study also shows that modern or historic earthquakes that induced liquefaction in the same region and whose locations and magnitudes are fairly well know can serve as calibration events for paleoearthquakes. Future efforts that could further improve the usefulness of liquefaction feature in paleoseismology include (1) the development of new techniques for dating liquefaction features directly, (2) case studies of modern earthquakes that focus on the site and spatial distributions of liquefaction feature as well as geotechnical properties of liquefaction sites and (3) more rigorous quantification of uncertainties associated with estimates of timing, source areas and magnitudes of paleoearthquakes.

Interpretation of Penetration Resistance for Back-analysis at Sites of Previous Liquefaction

Liquefaction and paleoliquefaction studies are being used increasingly to interpret ground motion parameters ( i.e. , acceleration distribution, earthquake magnitude, and epicentral location) in regions of the world that experience infrequent, but damaging, earthquakes. These studies are especially applicable when the most recent damaging earthquakes occurred prior to the development of ground-motion instrumentation. For example, Martin and Clough (1994) examined liquefaction features formed during the 1886 Charleston, South Carolina earthquake; Pond (1996) and Obermeier and Pond (1999) examined paleoliquefaction features formed during a number of paleoearthquakes in the Wabash Valley region along the Indiana–Illinois border; Dickenson and Obermeier (1998) and Obermeier and Dickenson (2000) examined paleoliquefaction features formed during the 1700 Cascadia earthquake of the Pacific Northwest; and Ellis and de Alba (1999) recently examined liquefaction features formed during the 1755 Cape Ann, Massachusetts earthquake. Many of these studies back-calculate seismic parameters using the results of penetration tests conducted long after the earthquake. The most common method to back-calculate a lower-bound peak ground surface acceleration is to use the lowest value of penetration resistance obtained at a historic or paleoliquefaction site in conjunction with a correlation for liquefaction resistance of sandy soils, e.g. , Seed et al. (1985) or Stark and Olson (1995). In some studies, the current value of penetration resistance is assumed to be the “representative” value for back-analysis ( e.g. , Pond, 1996), while in other studies corrections are made to the current value of penetration resistance prior to back-analysis ( e.g. , Ellis and de Alba, 1999). This paper examines some of the factors that affect the interpretation of a “representative” penetration resistance for back-analysis of seismic parameters. The interpretation of these factors is illustrated using an example historic liquefaction site. The back-calculated values of a max from the example case history show the sensitivity of the back-analysis …

USGS National Seismic Hazard Maps

The U.S. Geological Survey (USGS) recently completed new probabilistic seismic hazard maps for the United States, including Alaska and Hawaii. These hazard maps form the basis of the probabilistic component of the design maps used in the 1997 edition of the NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, prepared by the Building Seismic Safety Council and published by FEMA. The hazard maps depict peak horizontal ground acceleration and spectral response at 0.2, 0.3, and 1.0 sec periods, with 10%, 5%, and 2% probabilities of exceedance in 50 years, corresponding to return times of about 500, 1000, and 2500 years, respectively. In this paper we outline the methodology used to construct the hazard maps. There are three basic components to the maps. First, we use spatially smoothed historic seismicity as one portion of the hazard calculation. In this model, we apply the general observation that moderate and large earthquakes tend to occur near areas of previous small or moderate events, with some notable exceptions. Second, we consider large background source zones based on broad geologic criteria to quantify hazard in areas with little or no historic seismicity, but with the potential for generating large events. Third, we include the hazard from specific fault sources. We use about 450 faults in the western United States (WUS) and derive recurrence times from either geologic slip rates or the dating of pre-historic earthquakes from trenching of faults or other paleoseismic methods. Recurrence estimates for large earthquakes in New Madrid and Charleston, South Carolina, were taken from recent paleoliquefaction studies. We used logic trees to incorporate different seismicity models, fault recurrence models, Cascadia great earthquake scenarios, and ground-motion attenuation relations. We present disaggregation plots showing the contribution to hazard at four cities from potential earthquakes with various magnitudes and distances.

Issues in Using Liquefaction Features for Paleoseismic Analysis

Research Article| January 01, 1999 Issues in Using Liquefaction Features for Paleoseismic Analysis Stephen F. Obermeier; Stephen F. Obermeier U.S. Geological Survey Mail Stop 955 Reston, VA 20192 sobermei@usgs.gov (S.F.O.) Search for other works by this author on: GSW Google Scholar Eric C. Pond Eric C. Pond Western Technologies Inc. 8305 Washington Place, NE Albuquerque, NM 87113-1670 pond@flash.net (E.C.P.) Search for other works by this author on: GSW Google Scholar Seismological Research Letters (1999) 70 (1): 34–58. https://doi.org/10.1785/gssrl.70.1.34 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Stephen F. Obermeier, Eric C. Pond; Issues in Using Liquefaction Features for Paleoseismic Analysis. Seismological Research Letters 1999;; 70 (1): 34–58. doi: https://doi.org/10.1785/gssrl.70.1.34 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietySeismological Research Letters Search Advanced Search This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.

Paleoliquefaction studies along the Atlantic seaboard: Implications for long-term seismic hazard

The search for paleoliquefaction evidence of large prehistoric earthquakes is presently underway both within the epicentral area of the 1886 Charleston earthquake and elsewhere along the Atlantic seaboard. To date, no conclusive evidence of large prehistoric earthquakes originating outside of South Carolina has been found. However, in addition to liquefaction resulting from the 1886 earthquake, paleoliquefaction data indicate that perhaps as many as five prehistoric earthquakes greater than about M b 5.5 to 6.2 occurred near Charleston during Holocene times. Furthermore, the data suggest that past large earthquakes within coastal S.C. may have not been limited exclusively to the established Charleston epicentral area. The mean return period for large liquefaction associated earthquakes is about 600 years for the past four earthquake cycles. Since only about 100 years have elapsed since the 1886 event, the probability of a similar earthquake occurring within the next several decades is judged to be low. However, the hazard presented by smaller earthquakes should not be overlooked.