Evaluating How Well Active Fault Mapping Predicts earthquake surface-rupture locations

Earthquake surface-fault rupture location uncertainty is a key factor in fault displacement hazard analysis and informs hazard and risk mitigation strategies. Geologists often predict future rupture locations from fault mapping based on the geomorphology interpreted from remote-sensing data sets. However, surface processes can obscure fault location, fault traces may be mapped in error, and a future rupture may not break every fault trace. We assessed how well geomorphology-based fault mapping predicted surface ruptures for seven earthquakes: 1983 M 6.9 Borah Peak, 2004 M 6.0 Parkfield, 2010 M 7.2 El Mayor–Cucapah, 2011 M 6.7 Fukushima-Hamadori, 2014 M 6.0 South Napa, 2016 M 7.8 Kaikoura, and 2016 M 7 Kumamoto. We trained geoscience students to produce active fault maps using topography and imagery acquired before the earthquakes. A geologic professional completed a “control” map. Mappers used a new “geomorphic indicator ranking” approach to rank fault confidence based on geomorphologic landforms. We determined the accuracy of the mapped faults by comparing the fault maps to published rupture maps. We defined predicted ruptures as ruptures near a fault (50–200 m, depending on the fault confidence) that interacted with the landscape in a similar way to the fault. The mapped faults predicted between 12% to 68% of the principal rupture length for the studied earthquakes. The median separation distances between predicted ruptures and strong, distinct, or weak faults were 15–30 m. Our work highlights that mapping future fault ruptures is an underappreciated challenge of fault displacement hazard analysis—even for experts—with implications for risk management, engineering site assessments, and fault exclusion zones

Updated Segmentation Model of the Aceh Segment of the Great Sumatran Fault System in Northern Sumatra, Indonesia

We study the Aceh Fault segment, the northernmost segment of the Great Sumatran Fault in western Indonesia. The Aceh Fault segment spans 250 km long, passing through three districts: West Aceh, Pidie Jaya, and Aceh Besar, a region of ~546,143 population. The current segmentation model assumes that the Aceh Fault segment acts as a single fault segment, which would generate closer to an M8 earthquake. This estimation is inconsistent with the ~M6–7 historical earthquake data. We conduct a detailed active fault mapping using an ~8 m resolution digital elevation model (DEM) of DEMNAS and sub-m DEM data from UAV-based photogrammetry to resolve this fault’s segmentation model. Our study indicates that the Aceh Fault is active and that the fault segment can be further divided into seven sub-segments: Beutong, Kuala Tripa, Geumpang, Mane, Jantho, Indrapuri, and Pulo Aceh. The fault kinematics identified in the field is consistent with right-lateral faulting. Our study’s findings provide new information to understand the fault geometry and estimate potential earthquakes’ maximum magnitude along the Aceh Fault segment. These are important for the development of seismic hazard analysis of the area

Evidence for mechanical coupling and strong Indian lower crust beneath southern Tibet

How surface deformation within mountain ranges relates to tectonic processes at depth is not well understood. The upper crust of the Tibetan Plateau is generally thought to be poorly coupled to the underthrusting Indian crust because of an intervening low-viscosity channel. Here, however, we show that the contrast in tectonic regime between primarily strike-slip faulting in northern Tibet and dominantly normal faulting in southern Tibet requires mechanical coupling between the upper crust of southern Tibet and the underthrusting Indian crust. Such coupling is inconsistent with the presence of active ‘channel flow’ beneath southern Tibet, and suggests that the Indian crust retains its strength as it underthrusts the plateau. These results shed new light on the debates regarding the mechanical properties of the continental lithosphere, and the deformation of Tibet

Research on Comparison of the Maximum Dynamic Shear Modulus Test

AbstractDynamic soil modulus and damping ratio are the two basic parameters to describe dynamic deformation characteristics of the soil. There are three ways to obtain soil dynamics parameters i.e. field test, laboratory test, and calculating empirical. Silt loam samples were collected from Dongying area in this study. In order to get the maximum dynamic shear modulus, the following methods were adopted. The shear wave velocity was tested in field using single-hole method, and the maximum dynamic shear modulus capacity was obtained based on the calculation result of the shear wave velocity. The paper compared the results obtained by three methods and got some useful conclusions. The maximum dynamic shear modulus value calculated by field test was close to the corresponding value from the laboratory dynamic triaxial test, while the value obtained from the empirical formula was significantly lower. However, as the theory, method and collation of data for two kinds of tests were different, their test results were not exactly the same

Hammer Seismic Reflection Imaging in an Urban Environment

Subsurface characterization within urban centers is critically important for city planners, municipalities, and engineers to estimate groundwater resources, track contaminants, assess earthquake or landslide hazards, and many other similar objectives. Improving geophysical imaging methods and results, while minimizing costs, provides greater opportunities for city/project planners and geophysicists alike to take advantage of the improved characterization afforded by the particular method. Seismic reflection results can provide hydrogeologic constraints for groundwater models, provide slip rate estimates for active faults, or simply map stratigraphy to provide target depth estimate. While many traditional urban seismic transects have included the use of vibroseis sources to improve reflection signals and attenuate cultural noise, low-cost and high-quality near-surface seismic reflection data can be obtained within an urban environment using impulsive sources at a variety of scales and at production rates that can significantly exceed those of swept sources

Earthquake trend prediction using long short-term memory RNN

The prediction of a natural calamity such as earthquakes has been an area of interest for a long time but accurate results in earthquake forecasting have evaded scientists, even leading some to deem it intrinsically impossible to forecast them accurately. In this paper an attempt to forecast earthquakes and trends using a data of a series of past earthquakes. A type of recurrent neural network called Long Short-Term Memory (LSTM) is used to model the sequence of earthquakes. The trained model is then used to predict the future trend of earthquakes. An ordinary Feed Forward Neural Network (FFNN) solution for the same problem was done for comparison. The LSTM neural network was found to outperform the FFNN. The R^2 score of the LSTM is better than the FFNN’s by 59%

KASNO KVARTARNA AKTIVNOST SEGMENTA HARAMACHI FUTABA RASJEDA U SJEVEROISTOČNOM JAPANU UOČENA NA TEMELJU TOPOGRAFSKIH ANAGLIFSKIH SLIKA I ANALIZE SEDIMENATA JEZGRE BUŠOTINE

The Haramachi Fault segment in the northeastern part of Honshu Island, Japan, has mainly sinistral fault movements with minor reverse component within the Futaba Fault Zone in the northeastern Japan arc. The 2011 Mw 9.0 earthquake occurred off the Pacific coast of Tohoku which caused large crustal deformations. Despite being the closest active fault to the epicenter, very limited investigation has been conducted on the Futaba Fault Zone. Previous studies used smaller scale topographic maps and fault activity was estimated only from trenching and borehole investigations in the central part of the Haramachi Fault segment. Thus, geometry, kinematic, and recent tectonic activity of the fault segment is not well identified, especially in northern part. In this study, we use a combination of high-resolution DEMs (2-m and 5-m mesh), several types of topographic anaglyph images (slope, negative and positive openness), and conducted field survey to confirm remote sensing interpretation. Subtle surface expression of deformation associated with active faulting, such as deformed terrace risers, deflected drainages, and small fault scarps can now be identified more clearly. Several new fault strands in the northern part of the segment were found supported by fault outcrops found in the field confirming the recent activity of the fault system. The new estimation of the total length of the Haramachi segment produced from the approach of this study yields 25 km, which is capable of producing Mw 6.5 – 7.0 or Mjma 7.2 earthquakes if ruptures were to occur altogether in the future. Moreover, a shallow borehole survey and radiocarbon dating from the soil organic material has revealed the minimal timing estimation of the most recent faulting in the Haramachi segment to be 3694 ± 24 BP. This research provides a revised understanding of active fault distribution and deformation associated with the Haramachi segment and validates the timing of the most recent faulting event more broadly.Segment rasjeda Haramachi, dio je Fatuba rasjedne zone u sjeveroistočnom dijelu Japanskog luka, na otoku Honshu. Segment rasjeda Haramachi ukazuje uglavnom na lijeve pomake rasjeda s manjom reversnom komponentom. Potres intenziteta 9,0 Mw dogodio se 2011. godine u blizini pacifičke obale Tohokua koji je izazvao velike deformacije kore. Unatoč tome što predstavlja aktivni rasjed najbliži epicentru, u zoni rasjeda Futaba provedena su vrlo ograničena istraživanja. U prethodnim istraživanjima korištene su topografske karte manjeg mjerila, dok je aktivnost rasjeda procijenjena samo na temelju istraživanja izrađenih rovova i bušotinskih podataka u središnjem dijelu segmenta rasjeda Haramachi. Stoga, geometrija, kinematika, kao i nedavna tektonska aktivnost segmenta rasjeda nije dobro identificirana, osobito u sjevernom dijelu. U ovom istraživanju korištena je kombinacija DEM-ova visoke razlučivosti (mreža od 2 m i 5 m), nekoliko vrsta topografskih anaglifskih prikaza (nagib, negativna i pozitivna otvorenost), kao i terensko istraživanje kako bi se potvrdila interpretacija podataka dobivenih daljinskim istraživanjima. Neznantne površinski izražene deformacije povezane s aktivnim rasjedanjem, kao što su izdignute deformirane terase, pomaknute drenaže i mali pomaci rasjeda vidljivi na površini mogu se sada jasnije identificirati. Nedavna aktivnost rasjednog sustava vidljiva je kroz identifikaciju nekoliko novih rasjeda, čije je postojanje potkrijepljeno rezultatima terenskih istraživanja. Nova procjena ukupne duljine Haramachi segmenta dobivena pristupom iz ovog istraživanja iznosi 25 km, što može proizvesti potres od 6,5 – 7,0 Mw ili 7,2 Mjma. Štoviše, ispitivanje plitkih bušotina i datiranje ugljika iz organskog materijala tla otkrilo je minimalnu vremensku procjenu najnovijeg rasjedanja u Haramachi segmentu na 3694 ± 24 BP. Ovaj pristup revidirao je razumijevanje aktivne distribucije rasjeda i deformacija povezanih s Haramachi segmentom i potvrdio vrijeme najnovijeg događaja rasjedanja u širem smislu

Evaluation of The Current Level of Knowledge of The Residents of Dhaka City Regarding Earthquake Hazard

An earthquake is a sudden disaster that is not possible to predict. This impulsive behavior makes it very dangerous for humankind. Precautionary measures are immense for reducing damage. The first step of preventive measures for an earthquake is raising awareness. Dhaka City has a high earthquake risk due to its large population and urbanization. Researchers have said that an earthquake in this zone can be fatal, resulting in heavy casualties with structural damage. For this reason, proper awareness is essential for the residents of this area. This study shows an insight into the knowledge level of the residents of Dhaka City regarding earthquake incidents. Survey data indicates that many people lack Knowledge of what to do before and during an earthquake. Especially school and college-going students are unaware of the essential things to do during an earthquake incident. Many people still don’t know the importance of a seismic-resistant building system and are unprepared for a seismic event. This study brings these aspects together to learn about the knowledge level, which can help policymakers raise awareness among this city's residents

Seismic risk due to surface rupture : revision of legislations from different seismic regions of the world : proposal for Mendoza

El Gran Mendoza se encuentra en una región atravesada por fallas activas que han producido rupturas superficiales en el pasado y que pueden volver a producirla en el futuro, lo que constituye un peligro para construcciones realizadas sobre la traza de falla. La normativa de construcción sismorresistente vigente en Argentina es la establecida a nivel nacional, y no incluye el peligro por ruptura superficial, si bien sugiere incluirlo en el futuro de contarse con estudios que lo permitan. Con el objetivo de desarrollar regulaciones frente al peligro por ruptura superficial en Mendoza, en este trabajo se describen y analizan tres casos de estudio (California, Estados Unidos; Costa Rica; y Nueva Zelanda) cuyas experiencias pueden ser útiles para determinar criterios de zonificación. Teniendo en cuenta las lecciones aprendidas en estos tres países y las particularidades del caso mendocino, se busca de contribuir a lograr que la región sea más resiliente frente al peligro sísmico. La primera medida necesaria para esto es un programa sistemático de mapeo de fallas activas a escala adecuada. Relacionando los mapas con el uso de tierra (urbano, rural, de interfase), pueden determinarse los tipos de construcciones permitidos y no permitidos para evitar daños por ruptura superficial.The Great Mendoza is located in a region were active faults have produced surface ruptures in the past, and that may re-produce them in the future, which is a danger for constructions carried out on the fault trace. The regulations of seismorresistant construction in force in Argentina are the ones established at national level, and do not include the danger due to surface rupture, even though it is suggested to be included in the future if there are studies that allow it. With the purpose of developing regulations against danger caused by surface rupture in Mendoza, this work describes and analyzes three case studies (California, United States; Costa Rica; and New Zealand), experiences that can be useful to determine zoning. Taking into account the lessons learned in these three countries and the particularities of the Mendoza case, the aim of this work is to contribute to making the region more resilient in facing seismic risk. The first necessary measure for this is a systematic program of active fault mapping at an appropriate scale. The types of constructions allowed and not allowed to avoid damages by surface rupture can be determined by relating the maps to the land use (urban, rural, interphase).Fil: Mescua, José. Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA).Fil: Giambiagi, Laura. Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA)