Major earthquakes in continental regions may cause significant damage. Preexisting fault system across megacity receives high attention for possible seismic damages. Earthquake occurrence mechanism ...is important to assess the geohazard potentials. Continental‐scale Quaternary fault system is developed across the Seoul metropolitan area where the population is the largest in the Korean Peninsula. Historical seismic‐damage records suggest potential seismic hazards in the Seoul metropolitan area. We investigate the fault motions and spatial distribution of earthquakes in the Seoul metropolitan area using a matched‐filter technique that is based on stacked waveform crosscorrelation functions among densely‐deployed seismic stations. The analysis detects 1103 earthquakes that include 360 events with magnitudes (ML) of −0.6 to 2.0 around the Chugaryeong fault and 34 events with magnitudes of −0.5 to 2.7 around Wangsukcheon, Pocheon, and Yeseonggang faults. The seismicity suggests a set of near‐vertical subparallel (or orthogonal) faults that develop from the major faults. A major fault system behaves as a backbone structure that makes branch faults develop, producing seismicity including major earthquakes. The backbone structure may control the fault development that conforms to the ambient stress field. The backbone faults may play a role to increase geohazard potentials.
Plain Language Summary
The Seoul metropolitan area is the most populated region in the Korean Peninsula. Historical seismic damage records and major Quaternary faults suggest high seismic hazard potentials in the region. The identification of earthquake‐spawning faults is crucial for seismic hazard mitigation. We illuminate the earthquake‐spawning faults from micro to small earthquakes in the Seoul metropolitan. We perform a matched‐filter analysis to find earthquakes in adjacent locations of reported events. Recently‐deployed temporary dense seismic stations allow us to detect microearthquakes in high ambient‐noise environments of the megacity. We detect 1103 earthquakes that include 360 events with magnitudes (ML) of −0.6 to 2.0 around the Chugaryeong fault and 34 events with magnitudes (ML) of −0.5 to 2.7 around Wangsukcheon, Pocheon, and Yeseonggang faults. The earthquake distribution suggests the presence of active near‐vertical subparallel or conjugate faults along the major Quaternary faults that may behave as backbones of earthquake‐spawning faults.
Key Points
Micro to small earthquakes occur around Quaternary faults in the Seoul metropolitan area
Subvertical strike‐slip faults develop along the Quaternary faults, responding to the ambient stress field
Clustered earthquakes occur along conjugate or subparallel faults
Quaternary faults run across the Seoul metropolitan area that is the highest population region in the Korean Peninsula. Active fault identification and seismic hazard potential assessment are crucial ...for public safety. Densely deployed permanent and temporal seismic stations enabled us to detect micro to small earthquakes, allowing us to identify earthquake‐spawning faults in Seoul metropolitan area. The source parameters of 455 earthquakes in 2004–2020 are refined. The Gutenberg‐Richter b value is 0.94. Dominant focal depths are 4–15 km. The focal mechanism solutions of 64 earthquakes are determined using seismic‐wave polarities and amplitude ratios. Strike‐slip earthquakes are dominant in the region. Earthquakes are clustered around the Chugaryeong fault system. The dominant strikes of fault planes range from N20°E to N45°E in the northern and southern Seoul metropolitan areas, suggesting branch fault development locally. The earthquakes in middle‐northern Seoul present N‐S directional strike‐slip motions at depths ∼7.5 km along the Chugaryeong fault, suggesting seismically active near‐vertical faults subparallel with Chugaryeong fault.
Plain Language Summary
The Seoul metropolitan area is the largest population region in the Korean Peninsula. More than 20 million people live in the area where Quaternary faults run across. Historical literatures presented high seismic damages in the region. Active fault identification and seismic hazard potential assessment are crucial for public safety. Dense seismic stations were deployed to investigate the seismicity and earthquake‐spawning faults in the Seoul metropolitan area. We refined the source locations of 455 earthquakes in 2004–2020. The focal mechanisms solutions of 64 earthquakes were determined using the seismic‐wave polarities and amplitude ratios. Strike‐slip earthquakes are dominant in the region. The strikes of fault planes range from N20°E to N45°E in the northern and southern Seoul metropolitan areas. Branch faults appear to develop locally according to the ambient stress field. Microseismicity are clustered locally. The earthquakes in middle‐northern Seoul present N‐S directional strike‐slip motions at depths ∼7.5 km along the Chugaryeong fault. The Chugaryeong fault system appears to be seismically active.
Key Points
Earthquake‐spawning faults run across the Seoul metropolitan area
Chugaryeong fault behaves as a single continuous fault, producing earthquakes
Branch faults develop locally by the ambient stress field
We investigate the upper‐crustal seismic velocity structure in the Seoul metropolitan area, where about 20 million people live. The Chugaryeong fault zone (CFZ) is placed in this area, but the ...seismic hazard potential remains unclear. We conducted ambient noise tomography to illuminate the high‐resolution upper‐crustal structure in the Seoul metropolitan area. We analyzed continuous vertical seismic records for ∼5 months from a dense seismic array with 77 broadband stations. Group velocity dispersion curves and tomographic maps were extracted between 0.5 and 10 s periods. We inverted 3‐D group velocity tomography models up to a depth of ∼10 km from the group velocity maps. The shear‐wave velocity model is consistent with the geological features. High‐velocity anomalies at shallow depths are correlated with the surface topography and geology. The CFZ is located at a low velocity below the 5 km depth and presented as the simplified model. The large VS contrast regions are located beneath NS‐trending faults. The cross‐sections coincide with the near‐vertical strike‐slip faults in this area. In the southern region of the Seoul metropolitan area, low‐velocity anomalies correlate with high heat flow regions. Our results effectively suggest high resolution upper‐crustal structures and subsurface hidden faults in the urban area.
Plain Language Summary
The Chugaryeong fault zone (CFZ) runs across the Seoul metropolitan area, where more than 20 million people live. The Chugaryeong fault system was repeatedly reactivated in the Quaternary. This study investigates the upper crustal structures in the Seoul metropolitan area using ambient seismic tomography based on densely deployed seismic stations. The seismic velocity structures are correlated with surface topography and geology. Low velocities are present in the southern Seoul metropolitan area of high heat flows. Vertically consistent low shear‐wave velocity anomalies are observed at depths of 5–10 km in the CFZ. Lateral variations in seismic velocities reveal the fault structures, which is consistent with seismic activities. The lateral gradients of shear‐wave velocities illuminate the near‐vertical fault geometry. The upper‐crustal shear‐wave velocity model may provide information to assess seismic hazard potentials in the Seoul metropolitan area.
Key Points
High‐resolution upper‐crustal structures in urban region are derived from ambient noise tomography based on dense seismic stations
Ambient noise tomography reveals near‐vertical strike‐slip fault zones with low velocity anomalies in the Seoul metropolitan area
The fault zones run across the Seoul metropolitan area, producing earthquakes
This study was realized to evaluate the nutritional value of rice grains as a replacement for corn grains in the diet of growing Hanwoo steers.
Two experimental diets were prepared: i) Corn total ...mixed ration (TMR) consisting of 20% corn grains and ii) Rice TMR consisting of 20% rice grains, in a dry matter (DM) basis. These treatments were used for in vitro rumen fermentation and in vivo growth trials. In the rumen fermentation experiment, the in vitro DM digestibility (IVDMD), in vitro crude protein digestibility (IVCPD), in vitro neutral detergent fiber digestibility, pH, ammonia nitrogen, and volatile fatty acids (VFA) were estimated at 48 h, and the gas production was measured at 3, 6, 12, 24, and 48 h. Twenty four growing Hanwoo steers (9 months old; body weight BW: 259±13 kg) were randomly divided into two treatment groups and the BW, dry matter intake (DMI), average daily gain (ADG), and feed conversion ratio (FCR) were measured.
The in vitro experiment showed that the IVDMD, IVCPD, and VFA production of the Rice TMR were higher than those of the Corn TMR (p<0.05). The growth trial showed no differences (p>0.05) in the final BW, ADG, DMI, and FCR between the two TMRs.
The use of rice grains instead of corn grains did not exhibit any negative effects on the rumen fermentation or growth performance, thereby rice grains with a DM of less than 20% could be used as a starch source in the diet of growing steers.
An approximately 40‐km long high‐resolution reflection seismic profile (P3) was acquired in the metropolitan area of Seoul in South Korea for the purpose of fault system imaging in a highly noisy and ...challenging urban environment. Two 12t seismic vibrators (mini‐vibs) were used as the seismic source. Data were recorded using a dual element seismic spread; 20 m spaced 421 wireless seismic recorders connected to 10 Hz geophones and 20 micro‐electro‐mechanical‐based landstreamer sensors (2 m sensor spacing) attached to one of the vibrators. The purpose of the dual spread employed was to delineate both near‐surface and deep structures. The processing results show good quality and the processing work was complemented by different analysis to further constraints the geological interpretation. The survey results provide evidence for the 3D geometry of three fault systems, including Chugaryeong, Pocheon, and Wangsukcheon faults. A gently westerly dipping set of reflectivity underlying a dome‐shaped package of reflectivity is interpreted as a fault, and could project to the known surface position of the Pocheon fault. The dome‐shaped reflectivity is interpreted as folded and faulted dyke or sill systems. Downward continuation of the interpreted fault intersects the sub‐vertical Chugaryeong fault in a zone where the current seismicity is observed, suggesting that these two major fault systems may have jointly evolved in the form of splay faults. Reflections from the Wangsukcheon fault are also present in the data and interpreted to dip approximately 60° to the east, in an opposite direction to the two other faults.
Plain Language Summary
An approximately 40‐km long high‐resolution reflection seismic profile was acquired in the metropolitan area of Seoul in South Korea for the purpose of in‐depth fault system imaging in a highly noisy and challenging urban environment. Two different types of receivers were used simultaneously to achieve good results from both shallow and deep structures. Processing results have good quality and are complemented with different analysis to further constraints the geological interpretation. The survey results provide evidence for the 3D geometry of three fault systems, including Chugaryeong, Pocheon, and Wangsukcheon faults. A gently westerly dipping structure underlying a dome‐shaped structure is interpreted as a fault, and could project to the known surface position of the Pocheon fault. A dome‐shaped reflectivity is interpreted as folded and faulted dyke or sill systems. Downward continuation of the interpreted fault intersects the sub‐vertical Chugaryeong fault in a zone where the current seismicity is observed, suggesting that these two major fault systems may be connected and jointly evolved. Results from the Wangsukcheon fault are also present in the data and it is interpreted to approximately dip 60° to the east, in an opposite direction to the two other faults.
Key Points
Reflection seismic imaging of fault systems in Seoul metropolitan area
Suggested dependency of the regional seismicity from Chugaryeong fault system
Deep geometry reconstruction of three regional fault systems
Objective: This study aimed to identify the sagittal parameters associated with health-related quality of life and genetic variations that increase the risk of adult spinal deformity (ASD) onset in ...the older population.Methods: We recruited 120 participants who had a sagittal vertical axis > 50 mm in a sagittal imbalance study. Sagittal radiographic parameters, cross-sectional area, and intramuscular fatty infiltration using the Goutallier classification in the paraspinal lumbar muscles were evaluated. Functional scales included the self-reported Oswestry Disability Index (ODI), 36-item Short Form Health Survey (SF-36), and visual analogue scales (VAS) for back and leg pain. We performed whole-exome sequencing and an exome-wide association study using the 100 control subjects and 63 individuals with severe phenotypes of sagittal imbalance.Results: Pelvic incidence minus lumbar lordosis (PI–LL) mismatch was negatively associated with the SF-36 and positively correlated with ODI and VAS for back and leg pain. PI–LL was related to the quality and size of the paraspinal muscles, especially the multifidus muscle. We identified common individual variants that reached exome-wide significance using single-variant analysis. The most significant single-nucleotide polymorphism was rs78773460, situated in an exon of the SVIL gene (odds ratio, 9.61; p = 1.15 × 10-9).Conclusion: Older age, higher body mass index, and a more significant PI–LL mismatch were associated with unfavorable results on functional scales. We found a genetic variation in the SVIL gene, which has been associated with the integrity of the cytoskeleton and the development of skeletal muscles, in severe ASD phenotypes. Our results help to elucidate the pathogenesis of ASD.
Highlights AS patients had cervical spine fracture injuries after minor trauma, but OPLL patients mostly had spinal cord injuries without bony fractures. Improvement from neurologic deficit after ...proper surgical treatment showed better outcomes in AS and OPLL patients than in controls It is important to thoroughly examine patients with AS or OPLL after cervical trauma so as not to delay diagnosis.
This study was conducted to isolate the cellulolytic microorganism from the rumen of Holstein steers and characterize endoglucanase gene (
) from the isolated microorganism.
To isolate anaerobic ...microbes having endoglucanase, rumen fluid was obtained from Holstein steers fed roughage diet. The isolated anaerobic bacteria had 98% similarity with
(
) Ce2 (Accession number: AB163733). The
from isolated
sp. was cloned using the published genome sequence and expressed through the
BL21.
The maximum activity of recombinant
(
) was observed at 50°C and pH 4.0. The enzyme was constant at the temperature range of 20°C to 40°C but also, at the pH range of 3 to 9. The metal ions including Ca
, K
, Ni
, Mg
, and Fe
increased the endoglucanase activity but the addition of Mn
, Cu
, and Zn
decreased. The Km and Vmax value of
were 14.05 mg/mL and 45.66 μmol/min/mg. Turnover number, Kcat and catalytic efficiency, Kcat/Km values of
was 96.69 (s
) and 6.88 (mL/mg/s), respectively.
Our results indicated that
of
isolated from Holstein steers had a broad pH range with high stability under various conditions, which might be one of the beneficial characteristics of this enzyme for possible industrial application.
Subependymomas are slow-growing, benign neoplasms that are rarely found in the spinal cord. Because of the differences in the treatment plans, it might be very helpful for neurosurgeons to ...intraoperatively establish a diagnosis of spinal subependymoma, differentiated from other spinal intramedullary tumors. In this study, we analyzed frozen sections of spinal subependymomas to identify potential histological clues of spinal subependymomas to differentiate them from tumors that mimic spinal subependymoma. We reviewed the frozen sections and the corresponding permanent slides for 7 cases of spinal subependymoma. The spinal subependymomas showed several characteristic patterns, including, most importantly, an eccentric or both central and eccentric location in the axial plane. Histologically, they showed a (1) well-demarcated and multinodular mass with (2) low or moderate cellularity, (3) a microlobular pattern, and (4) small clusters of neoplastic cells. These features appear to be very specific to spinal subependymomas and could help differentiate them from ependymomas or astrocytomas. Although we might not be able to provide an exact diagnosis of all spinal subependymomas using these histological features, we hope that they help neuropathologists and neurosurgeons to adequately diagnose and treat spinal subependymomas.
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