Landslides Triggered by the 2016 Mw 7.8 Pedernales, Ecuador Earthquake: Correlations with ESI-07 Intensity, Lithology, Slope and PGA-h

We provide a dataset of the landslides induced by the 2016 Pedernales megathrust earthquake, Ecuador (Mw 7.8, focal depth of 20 km) and compare their spatial distribution with mapped bedrock lithology, horizontal peak ground acceleration (PGA-h) and the macroseismic intensity based on earthquake-induced environmental effects (ESI-07). We studied 192 coseismic landslides (classified as coherent, disrupted and lateral spreads) located in the epicentral area, defined by the VII to IXESI-07 isoseismals. Based on our findings, lahar deposits, tuffs and volcanoclastic units are the most susceptible to landslides occurrence. Alluvial plains with fluvial loose fine sand are the most susceptible setting for lateral spreading, with a maximum intensity of IXESI-07. The coherent landslides are frequently found in altered shale and siltstone geological units with moderate slopes (8°–16°), with typical intensity ranging between VII and VIIIESI-07. Our analysis draws a typical framework for slope movements triggered by subduction earthquakes in Ecuador. The most dangerous setting is the coastal region, a relatively highly urbanized area located near the epicenter and where liquefaction can trigger massive lateral spreading events. Coherent and disrupted landslides, dominating the more internal hilly region, can be triggered also in moderate slope settings (i.e., less than 10°). Indeed, the regression analysis between seismic intensity, PGA-h and landslide occurrence shows that most of the events occurred at PGA-h values between 0.4 g and 1.2 g, at a distance of 30 to 50 km from the rupture plane. Our database suggests that lithology and hillslope geometry are the main geological/geomorphological factors controlling coseismic landslides occurrence; while the distance from the rupture plane plays a significant role on determining the landslide size. Finally, we underline that coseismically-triggered landslides are among the most common environmental effects occurring during large subduction events that can be effectively used to properly evaluate the earthquake macroseismic field. The landslide inventory we compiled is suitable for assessing the vulnerability of physical environment from subduction earthquakes in Ecuador, and offers a primary data source for future worldwide analysis.

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A database of the environmental effects associated to the December 29th, 2020 Mw 6.4 Petrinja earthquake (Croatia)

10.5194/egusphere-egu21-16574 ◽

2021 ◽

Author(s):

Matija Vukovski ◽

Marko Budić ◽

Marko Špelić ◽

Josip Barbača ◽

Nikola Belić ◽

...

Keyword(s):

Environmental Effects ◽

Focal Depth ◽

Lateral Spreading ◽

Second Phase ◽

Surface Rupture ◽

Maximum Displacement ◽

Epicentral Area ◽

Ground Shaking ◽

Seismogenic Source ◽

Surface Ruptures

On December 29th, 2020, a strong Mw 6.4 earthquake hit central Croatia. The epicenter was located approximately 3 km southwest of Petrinja, and the intensity was estimated to VIII-IX EMS. The earthquake led to significant environmental effects related to earthquake magnitude, focal depth, and geological and geotechnical properties of the affected area. The Croatian Geological Survey (HGI-CGS) conducted extensive geological and geodetic surveys starting a few hours following the main shock to measure the earthquake&#8217;s effects, including those on infrastructures. Ten geologists from the Department of Geology carried out surveys from Decmber 31st, 2020 to January 7th, 2021 along the potential seismogenic source (inferred from geological maps and InSAR data) and in the wider epicentral area that suffered significant damage (e.g., Glina and Sisak). During a second phase, researchers from the University of Zagreb (PMF UniZG), Slovenia (GeoZS), Italy (INGV, ISPRA, U. Chieti) and France (CEREGE, IRSN) were mobilized to complete the observations. The collaboration with these geologists allowed to deepen the investigations and to bring further detail to quantify the effects. The surveys were then compiled based on data formats used by the European Community, namely those of the INGV EMERGEO team (Villani et al., 2017; for environmental effects including surface ruptures and liquefaction) and those of the SURE group (Baize et al., 2019 for surface ruptures). These observations revealed that the earthquake triggered a discontinuous, few km-long surface rupture with a maximum displacement of about 20 cm, which is consistent with the lower average of observations made on similar events (Wells and Coppersmith, 1994). Liquefaction spread over several tens of square kilometers mostly in river plains, the most distant being about 20 km from the epicenter (to be confirmed!). Other observed effects include lateral spreading, landslides, groundwater regime changes, rockfalls, and various infrastructure damage. The compilation of the acquired dataset into a unified database, consistent with database of other historical and recent events, is essential for establishing reliable empirical relations between geological effects and physical characteristics of earthquakes (magnitude, depth). This forms the basis for seismic hazard assessments, whether for &#8220;surface rupture&#8221;, &#8220;liquefaction&#8221;, or &#8220;ground-shaking&#8221; potential.

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The Gujarat, West India, earthquake (Jan 26th 2001). A geodynamic event in an intraplate compressional regime?

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.17234 ◽

2001 ◽

Vol 34 (4) ◽

pp. 1405

Author(s):

Γ. Δ. ΔΑΝΑΜΟΣ ◽

Ε. Λ. ΛΕΚΚΑΣ ◽

Σ. Γ. ΛΟΖΙΟΣ

Keyword(s):

Large Scale ◽

Lateral Displacement ◽

Indian Subcontinent ◽

Plate Boundary ◽

Horizontal Displacement ◽

Vertical Displacement ◽

Lateral Spreading ◽

Tectonic Deformation ◽

Epicentral Area ◽

Surface Ruptures

The Jan. 26, 2001, Ms=7.7 earthquake occurred in Gujarat region of W. India, which lies 200-400 Km away from the active plate boundary zone, between the Indian subcontinent and the Asian plate, along the India-Pakistan border and the Himalayan belt. An Ms=7.7±0.2 earthquake also occurred in the same region in 1819. A zone of co-seismic E-W surface ruptures, 30-40 Km long and 15-20 Km wide, observed near the epicentral area and seems to be associated with pre-existing reverse faults and thrust folds, which were partially reactivated during the recent earthquake. Except the reverse vertical displacement a significant right lateral displacement was also observed along these E-W surface ruptures. This Ms=7.7 seismic event has been also accompanied by a large scale flexural-slip folding, as the absence of significant co-seismic fault displacement and fault scarp shows. This type of compressional tectonic deformation is also confirmed by the focal mechanism of the earthquake and the seismo-tectonic "history" of the area. The NW-SE open cracks, also observed along the same zone, are associated with the right lateral horizontal displacement of the reactivated fault (or branch faults) and the development of local extensional stress field in the huge anticlinic hinges of the co-seismic flexural-slip folds. A large number of ground ruptures, failures and open cracks are also associated with extensive sand boils, liquefaction phenomena and lateral spreading.

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A Seismic Alert System for Oil & Gas Offshore Fields

10.2118/207296-ms ◽

2021 ◽

Author(s):

Pamela Poggi ◽

Emilia Fiorini ◽

Daniela Tonoli ◽

Francesca Ioele ◽

Eric John Parker ◽

...

Keyword(s):

Real Time ◽

Ground Motion ◽

Oil And Gas ◽

Focal Depth ◽

Threshold Values ◽

Alert System ◽

Ground Acceleration ◽

Gas Field ◽

Expected Values ◽

Earthquake Data

Abstract Objectives/Scope This paper presents an innovative web tool developed for the seismic monitoring of critical infrastructure. As an example, we describe an application for the ENI offshore facilities, Jangkrik and Merakes Fields Development, offshore Indonesia. Methods, Procedures, Process The system monitors reported seismic activity in a project area, and issues warnings when earthquakes detected may have directly or indirectly impacted facilities. Notifications allow the owner to optimize decisions regarding post-earthquake asset surveys and maintenance, avoiding the need for inspections in areas not significantly affected. A system of email alerts and a web based GIS platform provide the end-user with a tool to control its own assets. Results, Observations, Conclusions The purpose of the tool is to indirectly monitor earthquakes in an area and identify those which may have damaged the Oil and Gas facilities of interest. This identification requires accurate near real-time earthquake data such as date, time, location, magnitude, and focal depth. To this end, the system retrieves earthquake data from a qualified set of public seismic agencies. The system computes the expected values of shaking at the specific offshore facilities (platforms, subsea structures, pipelines, etc.). Calculations are based on sets of Ground Motion Prediction Equations (GMPEs) selected to match the seismotectonic environment. The expected values of seismic acceleration generated by an earthquake are compared with threshold values and a warning message is issued to the facilities supervisors when the ground acceleration exceeds design values. Threshold values related to secondary seismic effects (e.g., seismically induced landslides, debris flow) which could affect facilities integrity are also considered in the alert system. Threshold values are defined considering project seismic and geohazard documents, to summarize strong ground motion parameters that could potentially trigger damaging seismic geohazards, and project design documents to collect all data about seismic design of the assets. Monitoring intervals are defined based on the documentation screening. Several alarm levels are selected, based on the potential severity of earthquake effects. The more severe levels of ground motion, with high damage potential, can trigger recommendation for inspection. Novel/Additive Information Asset integrity and safety are key drivers in the offshore petroleum industry. Safety performance with respect to earthquakes is a fundamental issue in all seismic prone areas. The seismic alert system presented highlights, in near real time, earthquakes that are potentially critical for structures in an Oil and Gas field. This allows the owners to make quick decisions and plan necessary intervention regarding assets affected directly or indirectly by earthquakes. Exploiting the wide background of knowledge in engineering and geoscience and the modern availability of global earthquake data, the tool can provide useful assistance in managing asset integrity, regardless of the availability of local seismic networks or strong motion stations.

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Intensity Reassessment of the 2017 Pohang Earthquake Mw = 5.4 (South Korea) Using ESI-07 Scale

Geosciences ◽

10.3390/geosciences10110471 ◽

2020 ◽

Vol 10 (11) ◽

pp. 471

Author(s):

Sambit Prasanajit Naik ◽

Ohsang Gwon ◽

Sabina Porfido ◽

Kiwoong Park ◽

Kwangmin Jin ◽

...

Keyword(s):

Seismic Hazard ◽

Environmental Effects ◽

Land Use Planning ◽

Korean Peninsula ◽

Agricultural Land ◽

Seismic Intensity ◽

Substantial Contribution ◽

Intensity Scale ◽

Small Magnitude ◽

Epicentral Area

The earthquake environmental effects (EEEs) around the epicentral area of the Pohang earthquake (Mw-5.4) that occurred on 15 November 2017 have been collected and classified using the Environmental Seismic Intensity Scale (ESI-07 scale) proposed by the International Union for Quaternary Research (INQUA) focus group. The shallow-focus 15 November Pohang earthquake did not produce any surface rupture, but caused extensive secondary environmental effects and damage to life-line structures. This earthquake was one of the most damaging earthquakes during the instrumental seismic era of the Korean Peninsula. The EEEs included extensive liquefaction, ground cracks, ground settlement, localized rockfall, and variation of the water table. The main objective of this paper was to carry forward a comparative assessment of the Pohang earthquake’s intensity based on traditional macroseismic scales and the ESI-07 scale. With that objective, this study will also make a substantial contribution to any future revision of the ESI-07 scale, which mostly comprises case studies from Europe and South America. The comparison of the ESI-07 scale with traditional intensity scales similar to the intensity scale used by the Korean Meteorological Administration for the epicentral areas showed 1–2-degree differences in intensity. Moreover, the ESI scale provided a clearer picture of the intensity around the epicentral area, which is mostly agricultural land with a lack of urban units or buildings. This study urges the integration of the traditional and ESI-07 scale for such small magnitude earthquakes in the Korean Peninsula as well as around the world in future. This will predict seismic intensity more precisely and hence provide a more-effective seismic hazard estimation, particularly in areas of low seismic activity. The present study will also provide a useful and reliable tool for the seismic hazard assessment of similar earthquakes around the study area and land-use planning at a local scale considering the secondary effects.

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3D distinct element back-analysis (static and dynamic) of a reconstructed rock slope

10.5194/egusphere-egu21-9559 ◽

2021 ◽

Author(s):

Anne-Sophie Mreyen ◽

Léna Cauchie ◽

Mihai Micu ◽

Hans-Balder Havenith

Keyword(s):

Distinct Element ◽

Back Analysis ◽

Unknown Origin ◽

Lateral Spreading ◽

Structural Aspect ◽

Slope Failures ◽

Ground Acceleration ◽

River Diversion ◽

Seismic Region ◽

Vast Number

To better comprehend mechanisms at the origin of natural slope failures, a vast number of potential slope weakening and failure triggering factors ought to be considered. Especially for rather ancient slope failures, such factors can be difficult to identify and strongly depend on the regional to local climatic as well as seismo-tectonic context.An example of such ancient failure of unknown origin is the Balta rockslide that is located in the seismic region of Vrancea-Buzau, Romanian Carpathians. Even though more superficial landslides are found abundantly in the studied valley, the Balta failure stands out in terms of magnitude and observed geomorphological markers (profound detachment scarp, debris mass accumulation). During the last years, the Balta rockslide has been intensively studied with geophysical measurements (seismic and electrical methods) in order to characterise the landslide and in-situ rock material as well as the extensive dimension of the failure (with an estimated volume of 28.5-33.5 million m&#179;).In this work, we show the results of a numerical back-analysis of the Balta rockslide based on its reconstructed slope topography, implemented with 3D geomodelling, and on prior established geophysical and geomorphological studies; the reconstruction was furthermore conditioned by the morphology of neighbouring slopes in order to better constrain related uncertainties. The structural aspect of the anti-dip bedding of the sandstone dominated flysch slope was remodelled with 40&#176; dipping discontinuities, while 55&#176; dipping crossing discontinuities represent the main joint family observed in the field. The back-analysis was performed with the 3D distinct element code 3DEC (version 5.2, developed by Itasca) and aims at both, understanding static factors affecting slope stability, as well as the behaviour of the pre-failure slope if subjected to dynamic loading by using a synthetic Ricker multiplier as well as real earthquake acceleration data. The actual slope shape in its post-failure state could be approximated after 120 seconds of ground acceleration and is highlighted by lateral spreading of debris mass as well as towards the valley; the latter supposedly caused a temporary landslide dam formation, and possibly accounts for the river diversion observed in the field. This numerical approach furthermore allows us to outline the main controlling factors during seismic slope excitation that are predominated by topographic and structural site effects.

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Climate Change Induced Flood and Landslides and Farmer’s Adapatation Practices in Paddy Production: Evidence of Rural Hilly Nepal

10.20944/preprints201910.0049.v1 ◽

2019 ◽

Author(s):

Raghu Bir Bista ◽

Ranjan Kumar Dahal

Keyword(s):

Climate Change ◽

Indigenous Knowledge ◽

Adaptive Capacity ◽

Low Cost ◽

Primary Data ◽

Adaptive Behaviors ◽

Effective Measure ◽

Hilly Region ◽

Wall Construction ◽

And Behavior

Climate change is a buzzword in the world. Scientist has approved it as global warming with its projection of undesired and unpredicted frequent extreme events and their vulnerabilities not only at present but also at future. There is an assumption of occurrence of adaptive capacity and behavior of farmers in agriculture production activity at some extent to neutralize climate change vulnerabilities of flood and landslides on paddy production. This paper empirically examines the effects of climate change in paddy production and farmer’s adaptive behaviors to neutralize such climatic shocks and events in paddy production by employing CD production function based econometric model. The study employed primary data collected through 642 household surveys. The study finds that climatic shocks and events have huge loss (60%) in paddy production and revenue income in such plot where farmers have not indigenous knowledge and practices. But both small and larger farmers who have adaptive capacity and behavior with their indigenous knowledge have less loss in paddy production and revenue income, although they have heterogeneity in their socio economic characteristics (income, asset holding, literacy, experience, land holding and age). The farmers who have used adaptive behavior have indigenous knowledge and experiences including bamboo wall construction to control flood and landslides and seed change to resist climatic shocks and events. In hilly region, the farmers have not sufficient alternative measures, except both adaptive measures because of their poverty, illiteracy and remote locations. The study finds their higher effective level to minimize vulnerabilities to paddy production and revenue per farm plot, although these adaptive behaviors are cost effective and local entity. Comparatively, bamboo wall construction is more effective measure in the paddy production than others are (seed switch) to minimize the flooding materials from the flood and the landslides. Thus, low cost indigenous adaption behavior of farmers is effective measure to climate change and climate change induced disasters and events vulnerability in paddy production.

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Chile Strong Ground Motion Flatfile

Earthquake Spectra ◽

10.1193/102715eqs158dp ◽

2016 ◽

Vol 32 (4) ◽

pp. 2549-2566 ◽

Cited By ~ 11

Author(s):

Nicolas Bastías ◽

Gonzalo A. Montalva

Keyword(s):

Ground Motion ◽

Plate Boundary ◽

Peak Ground Velocity ◽

South American ◽

Ground Acceleration ◽

Data Set ◽

Intensity Measures ◽

South American Plate ◽

Rupture Plane ◽

Illapel Earthquake

The Nazca-South American plate boundary produces large-magnitude events (Mw > 8) every 20 years on the coast of Chile. This work describes a public ground motion database that contains 3,572 records from 477 earthquakes and 181 seismic stations, which includes the recent 2015 Mw 8.3 Illapel earthquake. The data set is controlled by subduction interface and inslab events. The oldest event included is Valparaiso (1985), and the magnitude span is 4.6–8.8 Mw. The source-to-site distance metrics reported are the closest distance to the rupture plane ( R rup), epicentral ( R epi) and hypocentral ( R hyp) distances, with a range for R rup from 20 to 650 km. Site characterization is based on V S30, ranging from 110 to 1,951 m/s. Intensity measures included are peak ground acceleration, spectral acceleration values from 0.01 to 10 s, Arias intensity, and peak ground velocity. Each record was uniformly processed component by component. A flatfile with the related metadata and the spectral accelerations from processed ground motions is available at NEEShub ( http://doi.org/10.17603/DS2N30J ; Bastías and Montalva 2015 ).

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Source mechanism and aftershock study of the Colima, Mexico earthquake of January 30, 1973

Bulletin of the Seismological Society of America ◽

10.1785/bssa0690061819 ◽

1979 ◽

Vol 69 (6) ◽

pp. 1819-1840

Author(s):

A. Reyes ◽

J. N. Brune ◽

Cinna Lomnitz

Keyword(s):

Plate Tectonics ◽

Focal Depth ◽

Large Earthquake ◽

Seismic Gap ◽

Fault Plane Solutions ◽

Epicentral Area ◽

Middle America Trench ◽

Source Dimensions ◽

Middle America ◽

Set Up

abstract The Colima earthquake (magnitude 7.5) occurred just inland from the Middle America Trench, 110 km south of the Volcan de Colima and 160 km southeast of Manzanillo, Colima, Mexico. Damage at several cities and towns was severe, 30 people were killed, and hundreds were injured. Four days after the earthquake, a six-station portable seismograph array was set up in the epicentral area as part of a cooperative program between UCSD, the University of Mexico, and the Mexican Federal Power Commission. From about 330 aftershocks recorded in the following 212 weeks, accurate locations were obtained for 50. One large aftershock had a magnitude of 6.2, the others range in local magnitude from 1.5 to 4.5. The locations outline a region approximately 90 km long and 60 km wide, in nearly the same location as the aftershock zone inferred by Kelleher et al. (1973) for the 1941 earthquake. The focal depth of the aftershocks (ranging from 2 to 30 km) and the fault-plane solutions for the main event indicated a shallow dipping thrust plane (about 30°). The seismic moment estimated from mantle rayleigh waves is 3 × 1027 dyne-cm. The pattern of aftershocks was used to estimate the source dimensions. From the moment and source dimensions the average slip was estimated to be about 1.4 m, corresponding to a stress drop of about 8 bars. The occurrence of this earthquake is discussed in terms of the general seismicity of the Middle America Trench, the convergence rate predicted by plate tectonics, and the use of seismic gap theory for earthquake prediction. The fact that this earthquake may have been in the zone of the 1941 earthquake rather than in the adjacent seismic gap, suggests that caution must be taken in using seismic gap theory to predict earthquakes in the region. It further suggests that in the adjacent seismic gap a large earthquake may be eminent, and thus the gap may be an important area for deploying seismic instruments.

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Performance of engineered timber structures in the Canterbury earthquakes

Bulletin of the New Zealand Society for Earthquake Engineering ◽

10.5459/bnzsee.44.4.394-401 ◽

2011 ◽

Vol 44 (4) ◽

pp. 394-401 ◽

Cited By ~ 1

Author(s):

Andrew Buchanan ◽

David Carradine ◽

Justin Jordan

Keyword(s):

New Zealand ◽

Structural Damage ◽

Lateral Spreading ◽

Life Safety ◽

Timber Structures ◽

Ground Acceleration ◽

Different Types ◽

Vertical Ground ◽

Short Time ◽

Water Tanks

The September 2010 and February 2011 earthquakes in Canterbury, New Zealand resulted in significant ground excitations that caused severe geotechnical effects and widespread structural damage. This paper outlines the various forms of damage to different types of engineered timber structures, including timber water tanks. Most of the damage resulted from lateral spreading and high levels of horizontal and vertical ground acceleration. The response of these building types is discussed. Engineered timber structures generally performed well both for life safety and serviceability, with most buildings ready for occupation within a short time following the events.

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Destructive M6.2 Petrinja Earthquake (Croatia) in 2020—Preliminary Multidisciplinary Research

Remote Sensing ◽

10.3390/rs13061095 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1095

Author(s):

Snježana Markušić ◽

Davor Stanko ◽

Davorin Penava ◽

Ines Ivančić ◽

Olga Bjelotomić Oršulić ◽

...

Keyword(s):

Peak Ground Acceleration ◽

Pannonian Basin ◽

Fault System ◽

Earthquake Ground Motion ◽

Ground Acceleration ◽

Epicentral Area ◽

Local Site ◽

Site Characteristics ◽

Complex Fault ◽

Collapsed Buildings

On 28 December 2020, seismic activity in the wider Petrinja area strongly intensified after a period of relative seismological quiescence that had lasted more than 100 years (since the well-known M5.8 Kupa Valley earthquake of 1909, which is known based on the discovery of the Mohorovičić discontinuity). The day after the M5 foreshock, a destructive M6.2 mainshock occurred. Outcomes of preliminary seismological, geological and SAR image analyses indicate that the foreshocks, mainshock and aftershocks were generated due to the (re)activation of a complex fault system—the intersection of longitudinal NW–SE right-lateral and transverse NE–SW left-lateral faults along the transitional contact zone of the Dinarides and the Pannonian Basin. According to a survey of damage to buildings, approximately 15% of buildings were very heavily damaged or collapsed. Buildings of special or outstanding historical or cultural heritage significance mostly collapsed or became unserviceable. A preliminary analysis of the earthquake ground motion showed that in the epicentral area, the estimated peak ground acceleration PGA values for the bedrock ranged from 0.29 to 0.44 g. In the close Petrinja epicentral area that is characterized by the superficial deposits, significant ground failures were reported within local site effects. Based on that finding and building damage, we assume that the resulting peak ground acceleration (PGAsite) values were likely between 0.4 and 0.6 g depending on the local site characteristics and the distance from the epicentre.

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