Sensitivity of Kansas Microearthquake Network

1983 ◽  
Vol 54 (2) ◽  
pp. 13-22
Author(s):  
Anne Frances Sheehan ◽  
Don W. Steeples
Keyword(s):  
Seismic Activity ◽  
Epicentral Distance ◽  
Geological Survey ◽  
Distance Graphs ◽  
Seismograph Station

Abstract This study explores the magnitude-versus-distance sensitivity of the Kansas Geological Survey (KGS) microearthquake network. The ability of each seismograph station to record earthquakes of various magnitudes as a function of epicentral distance is investigated, and a series of magnitude-versus-distance graphs results. The ability of the network to monitor seismic activity in eastern Kansas is excellent to magnitude 1.5 and is sufficient to detect events greater than magnitude 2.3 in western Kansas. Station detection radii for magnitude 1.5 events range from 145 km for the Emporia seismograph station (EMK) to 225 km at Tuttle Creek (TCK); and for a magnitude 2 event, from 245 km at EMK to 385 km at TCK. The sensitivities of the nine seismographs of the network are similar despite their widespread locations across eastern Kansas.

SEISMIC SURVEY IN THE REGION OF RECENT EARTHQUAKE ACTIVITY NEAR DENVER, COLORADO

Geophysics ◽  
1968 ◽  
Vol 33 (6) ◽  
pp. 915-925
Author(s):  
Ben F. Rummerfield ◽  
A. Peter Olson ◽  
D. B. Hoover
Keyword(s):  
Seismic Activity ◽  
Seismic Reflection ◽  
Geological Survey ◽  
Seismic Survey ◽  
Earthquake Activity ◽  
Precambrian Basement ◽  
Basement Complex

A seismic‐reflection survey was carried out near Denver, Colorado, for the U. S. Geological Survey, to determine if structures exist in the 12,000‐ft sedimentary section or in the Precambrian basement that might explain the recent earthquake activity. No major faults were revealed in the sedimentary section. Reflections from a steeply dipping horizon believed to be in the basement complex may be indicative of faulting; however, the magnitude cannot be ascertained, as reflection events cannot be correlated at these depths. The results of the survey suggest the possibility of monitoring and studying subsurface structural conditions and related parameters in regions of seismic activity and/or suspected zones of tectonic instability.

The determination of S-wave polarization angles for an earth model with crustal layering

1964 ◽  
Vol 54 (5A) ◽  
pp. 1429-1440 ◽  
Author(s):  
Otto Nuttli
Keyword(s):  
Epicentral Distance ◽  
Vertical Axis ◽  
Great Circle ◽  
Earth Model ◽  
Polarization Angle ◽  
Wave Surface ◽  
S Wave ◽  
Surface Motion ◽  
Seismograph Station ◽  
Great Circle Path

Abstract This paper presents a method for determining the polarization angle of S waves which takes account of the crustal layering at the seismograph station. Charts are given for four crustal models, corresponding to normal continental, thick, and thin crusts, which enable one to obtain the polarization angle at the top of the mantle beneath the seismograph station. The equations to be used for obtaining the polarization angle are tan ∈ = F h tan γ tan ∈ = F v tan δ where ε is the polarization angle, γ is the angle between the horizontal component of the S-wave surface motion and the great circle path at the station, δ is the angle between the vertical axis and the component of the S-wave surface motion in the plane transverse to the great circle path, and Fh and Fv are functions of wave period, epicentral distance, and the crustal structure at the seismograph station. Values of Fh and Fv for four crustal models are given in the paper.

Further study of the T phase*

1952 ◽  
Vol 42 (1) ◽  
pp. 37-51
Author(s):  
Maurice Ewing ◽  
Frank Press ◽  
J. L. Worzel
Keyword(s):  
Shallow Water ◽  
Travel Time ◽  
Epicentral Distance ◽  
Compressional Waves ◽  
Seismograph Station ◽  
T Phase

Abstract New data are presented in support of the conclusion that the T phase is propagated across oceans as compressional waves in the water. T phases from many circumpacific-belt shocks were recorded at the Honolulu seismograph station and at the Kaneohe and Point Sur SOFAR Stations, permitting the determination of oceanic velocity by simple division of epicentral distance by travel time since correction for land travel was unnecessary. The signals were much sharper and less prolonged than those previously studied. Very little scatter in the velocity was observed. Divergent views on the nature of T reported by other investigators are due to complications in path, travel time, and land correction introduced by the relatively large proportion of land (or shallow water) paths involved in the shocks which they have studied.

scholarly journals Seismic activity in Denmark: detection level and recent felt earthquakes

1969 ◽  
Vol 28 ◽  
pp. 41-44
Author(s):  
Trine Dahl-Jensen ◽  
Peter H. Voss ◽  
Tine B. Larsen ◽  
Søren Gregersen
Keyword(s):  
North Sea ◽  
Seismic Activity ◽  
Exclusive Economic Zone ◽  
Geological Survey ◽  
Seismic Events ◽  
Detection Level ◽  
Seismic Stations ◽  
Seismological Data ◽  
Natural Earthquakes

The Geological Survey of Denmark and Greenland (GEUS) records seismological data at six locations in Denmark (Fig. 1) and all data from these stations are manually reviewed for events like earthquakes and explosions. The identified events are analysed and located, in many cases using supporting data from stations outside Denmark. Seismic events have been recorded instrumentally in Denmark since 1929, but earthquakes felt in Denmark have been reported as far back as 1515 (Lehmann 1956; Gregersen et al. 1998; GEUS 2012). This article reports on the developments in detection level of both man-made events and natural earthquakes within the Danish Exclusive Economic Zone (EEZ) from 2000 to 2012. Changes in detection level are mainly due to the availability of data from new seismic stations in Sweden and Norway as well as from a GEUS test station at Gøttrup in NW Jylland. As a case study, the list of events on and around Bornholm is reviewed. Also described here are the reported intensities at two recent felt events in Denmark (North Sea magnitude 4.3 on 19 February 2010 and Kattegat magnitude 4.1 on 6 August 2012).

Local earthquakes in New England*

1937 ◽  
Vol 27 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Mary P. Collins
Keyword(s):  
New England ◽  
Surface Waves ◽  
Seismic Activity ◽  
Natural Activity ◽  
Local Earthquakes ◽  
Seismograph Station

Summary During 1934 and 1935, records of approximately 150 definitely local disturbances were obtained on the Benioff seismographs at the Harvard Seismograph Station. Because of a curious concentration in the daytime hours and the few earthquakes reported felt during this interval, an attempt was made to establish criteria by which records of blasts and of local earthquakes might be distinguished from each other. Three, the ratio of the maximum P to the maximum S, the character of the surface waves, and the angle of emergence are discussed. The records of 32 of these disturbances, well recorded on all three Benioff components, are described. It is concluded that, although some of New England's seismic activity is artificial, there is, nevertheless, a greater amount of natural activity than is ordinarily attributed to this region.

The Morgan Hill Earthquake of April 24, 1984—Strong-Motion Records

1985 ◽  
Vol 1 (3) ◽  
pp. 419-443 ◽  
Author(s):  
A. Gerald Brady ◽  
Anthony F. Shakal
Keyword(s):  
Epicentral Distance ◽  
Strong Motion ◽  
Geological Survey ◽  
Strong Motion Records ◽  
San Andreas

Seventy-two strong-motion accelerograph stations, mostly from within the permanent networks of the U. S. Geological Survey and the California Division of Mines and Geology, were triggered during the Morgan Hill earthquake, April 24, 1984. Among the more interesting of the records are the large acceleration (1.29g) at Coyote Lake dam, the Gilroy array spanning the region between the San Andreas and Calaveras faults, the record from Hall's Valley (epicentral distance 4 km), and records from buildings, a bridge, and a dam within 20 km of the epicenter. Digitized data from 16 stations are available on tape.

scholarly journals EARTHQUAKES AND GEOMAGNETIC DISTURBANCES

2020 ◽  
Vol 6 (4) ◽  
pp. 93-98
Author(s):  
Anatol Guglielmi ◽  
Boris Klain ◽  
Nadezhda Kurazhkovskaya
Keyword(s):  
Experimental Study ◽  
Magnetic Fields ◽  
Geomagnetic Activity ◽  
Seismic Activity ◽  
Geological Survey ◽  
Earthquake Catalog ◽  
Geomagnetic Disturbances ◽  
Strong Earthquakes ◽  
The Us ◽  
Alternating Magnetic Fields

The article addresses the problem of the connection of earthquakes with geomagnetic phenomena. We have carried out an experimental study using a method based, firstly, on the separation of periods of geomagnetic activity into extremely quiet and disturbed, and, secondly, on the description of seismic activity with an index called the global daily magnitude (GDM). By analyzing the NEIC earthquake catalog of the US Geological Survey over a 20-year period from 1980 to 1999, we have shown that the planetary activity of earthquakes under extremely quiet geomagnetic conditions is noticeably higher than under disturbed conditions. The detected tendency for seismic activity to increase in extremely quiet periods of geomagnetic activity has indirectly been confirmed by the analysis of 35 earthquakes with magnitude 8 and higher, which occurred on Earth from 1980 to 2019. We have found that in extremely quiet geomagnetic conditions, the probability of the occurrence of strong earthquakes is noticeably higher. The result qualitatively confirms the assumption of a change in the regime of seismic activity due to the influence of alternating magnetic fields on the ductility of rocks.

scholarly journals GENETIC TYPES OF THE EXOGENOUS GEOLOGICAL PROCESSES, CHARACTERISTIC FOR THE MOUNTAIN TERRITORIES OF THE CENTRAL CAUCASUS AND THE STATE OF THE UNDERGROUND FRESH WATERS QUALITY

2016 ◽  
Author(s):  
Л.Н. Невский ◽  
Н.И. Невская ◽  
Х.О. Чотчаев
Keyword(s):  
Seismic Activity ◽  
Current Data ◽  
The State ◽  
Geological Survey ◽  
Information Support ◽  
North Caucasus ◽  
Engineering Structures ◽  
Mountain Areas ◽  
The North ◽  
Geological Processes

В работе обобщены результаты многолетних наблюдений за экзогенными геологическими процессами в ходе длительного периода геологоразведочных исследований различного назначения на всей территории осетинского сегмента Центрального блока Большого Кавказа. Перечислены основные типы экзогенных геологических процессов (ЭГП), характерные для высокогорных территорий Северного Кавказа. Дано определение системы государственного мониторинга состояния недр (ГМСН), как способа информационного обеспечения органов государственного управления недрами и других органов  государственной власти текущими данными, необходимыми для принятия решений по рациональному и безопасному недропользованию и планированию геологоразведочных работ. Исследована зависимость ЭГП от сейсмической активности. Показаны примеры антропогенного провоцирования ЭГП при игнорировании требований инженерно-геологических изысканий для трассирования инженерных линий и мест выбора строительных площадок под  инженерные сооружения на горных территориях. Показана зависимость ЭГП  от высотной зональности и техногенного вмешательства в естественные ландшафтные условия местности. В работе использованы материалы специализированных наблюдений по Северной Осетии территориальным центром ГМСН Южного федерального округа, по подсистемам «Экзогенные геологические процессы» и «Подземные воды».  Results of many years exogenous geological processes observations in the course of the continuance of geological survey studies of different designation in the entire territory of the large Caucasus central block Ossetic segment are generalized. Basic types of Exogenous Geological Processes (EGP) are enumerated, typical for the alpine territories of the North Caucasus. EGP dependence on the seismic activity is investigated. Definition of State Monitoring of the Depths State (SMDS) system is given as the information support method by current data of the state administration agency of mineral resources and other agencies, necessary for decision making by rational and safe subsoil use and geological survey works planning. The dependence of the EGP on seismic activity is investigated. The examples of anthropogenic provoking of EGP while ignoring the requirements of engineering and geological surveys for tracing service lines and selection areas for building sites of engineering structures in mountain areas are given. Examples of the EGP anthropogenic provocation are shown during ignoring of the geological engineering searches requirements for the tracing of engineering lines and places of the construction sites selection for civil constructions in the mountain territories. EGP dependence on the highaltitude zonality and the technogenic interference in the natural topographical locality conditions is shown. SMDS territorial center materials of the North Osetia specialized observations of Southern Federal region subsystems «Exogenous Geological Processes» and «Underground Waters» are used.

scholarly journals EARTHQUAKES AND GEOMAGNETIC DISTURBANCES

2020 ◽  
Vol 6 (4) ◽  
pp. 80-83
Author(s):  
Anatol Guglielmi ◽  
Boris Klain ◽  
Nadezhda Kurazhkovskaya
Keyword(s):  
Experimental Study ◽  
Magnetic Fields ◽  
Geomagnetic Activity ◽  
Seismic Activity ◽  
Geological Survey ◽  
Earthquake Catalog ◽  
Geomagnetic Disturbances ◽  
Strong Earthquakes ◽  
The Us ◽  
Alternating Magnetic Fields

The article addresses the problem of the connection of earthquakes with geomagnetic phenomena. We have carried out an experimental study using a method based, firstly, on the separation of periods of geomagnetic activity into extremely quiet and disturbed, and, secondly, on the description of seismic activity with an index called the global daily magnitude (GDM). By analyzing the NEIC earthquake catalog of the US Geological Survey over a 20-year period from 1980 to 1999, we have shown that the planetary activity of earthquakes under extremely quiet geomagnetic conditions is noticeably higher than under disturbed conditions. The detected tendency for seismic activity to increase in extremely quiet periods of geomagnetic activity has indirectly been confirmed by the analysis of 35 earthquakes with magnitude 8 and higher, which occurred on Earth from 1980 to 2019. We have found that in extremely quiet geomagnetic conditions, the probability of the occurrence of strong earthquakes is noticeably higher. The result qualitatively confirms the assumption of a change in the regime of seismic activity due to the influence of alternating magnetic fields on the ductility of rocks.

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