Analysis of the Seismicity in the Jalisco Block from June to December 2015

2019 ◽  
Author(s):  
Tatiana Marín‐Mesa ◽  
Francisco J. Núñez‐Cornú ◽  
Carlos Suárez‐Plascencia
Keyword(s):  
Seismogenic Zone ◽  
Regional Studies ◽  
Northern Coast ◽  
Jalisco Block ◽  
Seismic Swarms ◽  
Using Data ◽  
Dip Angle ◽  
Seismic Networks ◽  
Rivera Plate ◽  
Hypocentral Distribution

ABSTRACT We present the first study of seismicity in the region of the Jalisco Block using data recorded by the Jalisco Seismic Accelerometric Telemetric Network between June and December 2015. During this period, 683 local earthquakes with magnitudes between 1.0<ML≤4.0 were identified and relocated with Hypo71PC. From this catalog, we identify a heterogeneous hypocentral distribution with six continental crustal seismogenic areas. We also observed seismicity associated with the subduction process that extends 180 km from the Mesoamerican trench, which suggests an estimated dip angle of the slab between 22° and 31°. A subtle dip also suggests oblique subduction toward the Colima rift zone and bending of the Rivera plate. These observations are in agreement with previous partial regional studies using local seismic networks. Two seismic swarms were observed in this period, one in the Bahia de Banderas seismogenic zone, and a second in the Guadalajara Metropolitan zone. We note two areas on the northern coast of Jalisco with meager rates of seismicity.

scholarly journals Dip angles of active faults from the surface to the seismogenic zone inferred from a 2D numerical analysis of visco-elasto-plastic models: a case study for the Osaka Plain

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hayami Nishiwaki ◽  
Takamoto Okudaira ◽  
Kazuhiko Ishii ◽  
Muneki Mitamura
Keyword(s):  
Urban Areas ◽  
Active Faults ◽  
Three Dimensional ◽  
Seismogenic Zone ◽  
Earthquake Ground Motion ◽  
Convex Curve ◽  
Seismic Reflection Profile ◽  
Geological Structures ◽  
Dimensional Distribution ◽  
Dip Angle

AbstractThe geometries (i.e., dip angles) of active faults from the surface to the seismogenic zone are the most important factors used to evaluate earthquake ground motion, which is crucial for seismic hazard assessments in urban areas. In Osaka, a metropolitan city in Japan, there are several active faults (e.g., the Uemachi and Ikoma faults), which are inferred from the topography, the attitude of active faults in surface trenches, the seismic reflection profile at shallow depths (less than 2 km), and the three-dimensional distribution of the Quaternary sedimentary layers. The Uemachi and Ikoma faults are N–S-striking fault systems with total lengths of 42 km and 38 km, respectively, with the former being located ~ 12 km west of the latter; however, the geometries of each of the active faults within the seismogenic zone are not clear. In this study, to examine the geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone, we analyze the development of the geological structures of sedimentary layers based on numerical simulations of a two-dimensional visco-elasto-plastic body under a horizontal compressive stress field, including preexisting high-strained weak zones (i.e., faults) and surface sedimentation processes, and evaluate the relationship between the observed geological structures of the Quaternary sediments (i.e., the Osaka Group) in the Osaka Plain and the model results. As a result, we propose geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone. When the friction coefficient of the faults is ~ 0.5, the dip angles of the Uemachi and Ikoma faults near the surface are ~ 30°–40° and the Uemachi fault has a downward convex curve at the bottom of the seismogenic zone, but does not converge to the Ikoma fault. Based on the analysis in this study, the dip angle of the Uemachi fault zone is estimated to be approximately 30°–40°, which is lower than that estimated in the previous studies. If the active fault has a low angle, the width of the fault plane is long, and thus the estimated seismic moment will be large.

scholarly journals Comparative Analysis of Distribution of Intertidal Fish Assemblages in Different Estuarine Systems on Northern Coast of Brazil

2017 ◽  
Vol 10 (2) ◽  
pp. 26 ◽  
Author(s):  
Milton Goncalves Silva Junior ◽  
Antonio Carlos Leal Castro ◽  
Ulrich Saint-Paul
Keyword(s):  
Comparative Analysis ◽  
Fish Assemblages ◽  
Coastal Region ◽  
Fish Fauna ◽  
Estuarine Fish ◽  
Northern Coast ◽  
Tidal Creeks ◽  
Estuarine Systems ◽  
Using Data ◽  
High Dynamics

The northern coast of Brazil has more than 30 estuaries distributed along 650 km of coastline. These conditions favor the presence of relatively large fish communities in estuarine environments, but published information on the fish fauna in tidal creeks in northern Brazil is only available for some mangrove systems, and comparative studies between fish estuarine communities in different tidal creeks are less common. The choice of the study area was based on the fact that it has been poorly investigated with regard to estuarine fish fauna in comparison in mangrove tidal creeks using the same fishing gear. The objective of the present study was to compare the composition of the relative biomass of taxonomic, functional and ecological guilds of fish assemblages occurring in estuarine systems along the northern coast of Brazil. The study area of the present comparative analysis extended from the southeastern edge of the Marajoara Gulf to the western edge of the Maranhense Gulf. A comparative analysis among different estuarine systems was performed using data from other studies. The abundance of juveniles was greater in the Caeté, Curuçá and Cururuca estuaries than other estuaries. Cluster analysis separated the estuaries into two distinct groups and significant differences between these groups only exist in relation to geographical proximity. The present investigation indicates that the coastal region between the states of Pará and Maranhão is characterized by high dynamics and environmental heterogeneity, particularly with regard to changes in river discharge and tidal fluctuations. The present results underscore the importance of ecological information on ichthyofauna in tropical estuaries in order to include appropriate descriptors in conservation or restoration processes of marine communities and habitats.

Site fidelity and residence times of humpback whales (Megaptera novaeangliae) on the Brazilian coast

2012 ◽  
Vol 92 (8) ◽  
pp. 1783-1791 ◽  
Author(s):  
Clarêncio G. Baracho-Neto ◽  
Elitieri Santos Neto ◽  
Marcos R. Rossi-Santos ◽  
Leonardo L. Wedekin ◽  
Mariana C. Neves ◽  
...  
Keyword(s):  
Residence Time ◽  
Site Fidelity ◽  
Megaptera Novaeangliae ◽  
Humpback Whales ◽  
Brazilian Coast ◽  
Northern Coast ◽  
Occupancy Rate ◽  
Breeding Grounds ◽  
Minimum Number ◽  
Using Data

Humpback whales (Megaptera novaeangliae) migrate between their feeding grounds, located in high latitudes, and their breeding grounds, located in low latitudes, exhibiting certain levels of site fidelity to their migratory destinations. The residence time, also known as occupancy rate, can be defined as the minimum number of days that those individuals remained in the same area. In this paper, site fidelity and residence time of humpback whales that breed off the northern coast of Bahia, Brazil were investigated. Data were collected between 2000 and 2009 on-board research cruises and whale watching vessels. This paper also studies possible differences between males and females with respect to site fidelity off the Brazilian coast, using data collected since 1989. A total of 841 whales were photo-identified. The vast majority of the whales (96%, N = 809) were seen only once in the studied area, while 4% (32 individuals) were seen twice. Most of the resights occurred within the same season (72%, N = 23), while 9 resights (28%) occurred in different years. None of the individuals were seen more than twice. The average site fidelity rate was 1% and the occupancy rate varied from one up to 21 days (mean = 5.3; SD = 5.4, N = 23).

Steep subduction geometry of the Rivera Plate beneath the Jalisco Block in western Mexico

1993 ◽  
Vol 20 (21) ◽  
pp. 2391-2394 ◽  
Author(s):  
Mario Pardo ◽  
Gerardo Suárez
Keyword(s):  
Western Mexico ◽  
Jalisco Block ◽  
Rivera Plate

scholarly journals Automatic moment tensor determination for the Hellenic Unified Seismic Network.

2016 ◽  
Vol 47 (3) ◽  
pp. 1308
Author(s):  
N. Triantafyllis ◽  
E. Sokos ◽  
A. Ilias
Keyword(s):  
Real Time ◽  
Seismic Station ◽  
Moment Tensor ◽  
Broad Band ◽  
Seismic Network ◽  
Global Networks ◽  
First Case ◽  
Inversion Procedure ◽  
Using Data ◽  
Seismic Networks

Modern seismic networks with broadband sensors and real time digital telemetry made Moment Tensor (MT) determination a routine procedure. Automatic MT’s are now provided by global networks and a few very dense regional networks, within minutes after a significant event. An automatic MT determination wasn’t possible for the broader Hellenic area since seismic station density wasn’t sufficient. The creation of the Hellenic Unified Seismic Network (HUSN) provided the opportunity to apply an automated MT procedure using the available broad band data from almost    one hundred stations. Thus the ISOLA code was extended towards the automatic operation based on Linux OS shell scripts, stand alone Fortran codes and SAC2000. Software supports both manual and automatic mode; at the first case, the user manually runs the program with the desired input parameters while at the latter, the system monitors a mailbox or RSS feed and if it receives an appropriate notification triggers the MT inversion procedure based on certain conditions. As it is setup now it calculates automatically the moment tensor of earthquakes larger than 3.5M  w using data from HUSN. Application of an automated MT inversion procedure for HUSN will provide important real time information for studies like ground motion evaluation, tsunami warning etc.

scholarly journals Evaluation of Dip Angles of Active Faults Beneath the Osaka Plain Inferred from a 2D Numerical Analysis of visco-elasto-plastic Models

2020 ◽  
Author(s):  
Hayami Nishiwaki ◽  
Takamoto Okudaira ◽  
Kazuhiko Ishii ◽  
Muneki Mitamura
Keyword(s):  
Fault Zone ◽  
Urban Areas ◽  
Active Faults ◽  
Three Dimensional ◽  
Seismogenic Zone ◽  
Earthquake Ground Motion ◽  
Convex Curve ◽  
Seismic Reflection Profile ◽  
Geological Structures ◽  
Dip Angle

Abstract The geometries (i.e., dip angles) of active faults from the surface to the seismogenic zone are among the most important factors used to evaluate earthquake ground motion, which is crucial to seismic hazard assessments in urban areas. In Osaka, a metropolitan city in Japan, there are several active faults (e.g., the Uemachi and Ikoma faults), which are inferred from the topography, the attitude of active faults in surface trenches, the seismic reflection profile at shallow depths (less than 2 km), and the three-dimensional distribution of the Quaternary sedimentary layers. The Uemachi and Ikoma faults are N–S-striking fault systems with total lengths of 42 km and 38 km, respectively, with the former being located ~12 km west of the latter; however, the geometries of each of the active faults within the seismogenic zone is not clear. In this study, to examine the geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone, we analyze the development of the geological structures of sedimentary layers based on numerical simulations of a two-dimensional visco-elasto-plastic body under a horizontal compressive stress field, including preexisting linear high-strained weak zones (i.e., faults) and surface sedimentation processes, and evaluate the relationship between the observed geological structures of the Quaternary sediments (i.e., the Osaka Group) in the Osaka Plain and the model results. Based on a comparison between the simulation results and the geological observations/interpretation, we propose geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone. When the friction coefficient of the faults is ~0.5, the dip angles of the Uemachi and Ikoma faults near the surface are ~30°–40° and the Uemachi fault has a downward convex curve at the bottom of the seismogenic zone but does not converge to the Ikoma fault. Based on the analysis in this study, the dip angle of the Uemachi fault zone is estimated to be approximately 30°–40°, and the downward extension of the Uemachi fault zone nearly coincides with the epicenter of the 2018 northern Osaka earthquake.

scholarly journals Multichannel Seismic Imaging of the Rivera Plate Subduction at the Seismogenic Jalisco Block Area (Western Mexican Margin)

2016 ◽  
Vol 173 (10-11) ◽  
pp. 3575-3594 ◽  
Author(s):  
Rafael Bartolome ◽  
Estefanía Górriz ◽  
Juanjo Dañobeitia ◽  
Diego Cordoba ◽  
David Martí ◽  
...  
Keyword(s):  
Seismic Imaging ◽  
Jalisco Block ◽  
Block Area ◽  
Rivera Plate ◽  
Plate Subduction

scholarly journals The Extended Continental Crust West of Islas Marías (Mexico)

2021 ◽  
Vol 9 ◽  
Author(s):  
Diana Núñez ◽  
Jorge A. Acosta-Hernández ◽  
Felipe de Jesús Escalona-Alcázar ◽  
Simone Pilia ◽  
Francisco Javier Núñez-Cornú ◽  
...  
Keyword(s):  
Continental Crust ◽  
Contact Region ◽  
Complex Structure ◽  
Sedimentary Basins ◽  
North American Plate ◽  
Seismic Profiles ◽  
Tectonic Structures ◽  
Jalisco Block ◽  
Rivera Plate ◽  
Plate Subduction

The crustal structure around the Islas Marías Archipelago has been debated for a long time. An important unresolved question is where the Rivera-North American plate subduction ends and the Tamayo fracture zone begins, from SE to NW. Results from the TsuJal project have shed light on the northwesternmost part of the Jalisco block structure. It is now clear that Sierra de Cleofas and the Islas Marías Escarpment comprise the northwestern continuation of the Middle America trench. However, other questions remain. In this paper, we present the structure of the shallow and deep crust and the upper mantle of the Islas Marías western region through the integration of multichannel seismic reflection, wide-angle seismic bathymetric and seismicity data, including records of an amphibious seismic network, OBS, and portable seismic stations, purposely deployed for this project, providing an onshore-offshore transect of 310 km length. Our findings disclose new evidence of the complex structure of the Rivera plate that dips 8°–9° underneath the NW Jalisco block as revealed by two seismic profiles parallel to the Islas Marías Escarpment. Moreover, we find five sedimentary basins and active normal faults at the edges of tectonic structures of the E-W oriented West Ranges and the N-S trending Sierra de Cleofas. Furthermore, the Sierra de Cleofas is the beginning of the active subduction of the Rivera plate beneath North America. The oceanic crust thickens and submerges towards the south while is coupled with the continental crust, from 6 km at the northern ends of the seismic profiles to 15 km in the contact region and 24 km at the coast and southern ends of them. The continental Moho was not fully characterized because of the geometry of the seismic transects, but a low-velocity layer associated with Rivera Plate subduction was observed beneath the Jalisco Block. Our results constrain the complexity of the area and reveal new structural features from the oceanic to continental crust and will be pivotal to assess geohazards in this area.

The Importance of Regional Seismic Networks in Monitoring Nuclear Test-Ban Treaties

2019 ◽  
Vol 91 (2A) ◽  
pp. 573-580 ◽  
Author(s):  
Keith D. Koper
Keyword(s):  
Detection Threshold ◽  
Nuclear Test ◽  
Global Networks ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Using Data ◽  
Seismic Networks ◽  
Test Ban ◽  
Nuclear Test Ban

Abstract The Comprehensive Nuclear-Test-Ban Treaty (CTBT) prohibits the testing of all nuclear weapons, no matter how small. Although the CTBT is not yet in force, its verification is supported by the International Monitoring System (IMS), which is about 90% complete. Using IMS data, seismologists are able to detect well-coupled underground nuclear explosions with yields larger than ∼0.5–1  kt anywhere in the world with high confidence. Lowering the detection threshold significantly, say to yields of 10−4–10−1  kt fully coupled, will require augmenting IMS data with records from thousands of seismometers that are deployed in various regional, national, and global networks. It will also require routine analysis (detection, location, and characterization) of small seismic events (M 0–3) that are well recorded only at local distances (&lt;150–200  km). This is the same problem faced by operators of regional seismic networks, who are tasked with developing earthquake catalogs as complete as possible without contamination from explosions and other nonearthquake sources. In the future, verification seismology is likely to become increasingly intertwined with the data, methods, and expertise of regional seismic network operators. Here, I highlight some of the important contributions to verification seismology that have recently been made using data recorded by regional seismic networks in North America, with a focus on small events recorded at local distances.

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