scholarly journals The 1934 Pahiatua earthquake sequence

1999 ◽  
Vol 32 (4) ◽  
pp. 221-245 ◽  
Author(s):  
Gaye Downes ◽  
David Dowrick ◽  
Euan Smith ◽  
Kelvin Berryman
Keyword(s):  
Body Wave ◽  
Active Faults ◽  
Stable Solution ◽  
Fault Rupture ◽  
Wave Modelling ◽  
Slip Mechanism ◽  
Isoseismal Map ◽  
The Town ◽  
Privately Owned ◽  
Moderate Magnitude

Descriptive accounts and analysis of local seismograms establish that the epicentre of the 1934 March 5 Ms7.6 earthquake, known as the Pahiatua earthquake, was nearer to Pongaroa than to Pahiatua. Conspicuous and severe damage (MM8) in the business centre of Pahiatua in the northern Wairarapa led early seismologists to name the earthquake after the town, but it has now been found that the highest intensities (MM9) occurred about 40 km to the east and southeast of Pahiatua, between Pongaroa and Bideford. Uncertainties in the location of the epicentre that have existed for sixty years are now resolved with the epicentre determined in this study lying midway between those calculated in the 1930's by Hayes and Bullen. Damage and intensity summaries and a new isoseismal map, derived from extensive newspaper reports and from 1934 Dominion Observatory "felt reports", replace previous descriptions and isoseismal maps. A stable solution for the epicentre of the mainshock has been obtained by analysing phase arrivals read from surviving seismograms of the rather small and poorly equipped 1934 New Zealand network of twelve stations (two privately owned). The addition of some teleseismic P arrivals to this solution shifts the location of the epicentre by less than 10 km. It lies within, and to the northern end of, the MM9 isoseismal zone. Using local instrumental data larger aftershocks and other moderate magnitude earthquakes that occurred within 10 days and 50 km of the mainshock have also been located. Approximate locations of other associated moderate magnitude earthquakes until October 1934 have been identified by their maximum intensity and S-P intervals read from the Wellington Wood-Anderson seismograph records. The distribution of S-P intervals of aftershocks (magnitudes M > 3.5) within 24 hours of the mainshock is used to delineate the probable mainshock rupture zone. Neither contemporary sources nor recent inquiries directed to old residents yield historical evidence of a surface fault rupture. Nevertheless, the strike-slip mechanism at 20 km depth determined by preliminary teleseismic body wave modelling of Doser and Webb suggests that rupture could have extended to the surface. Recent investigation of two of the freshest-looking, active faults that lie within the MM9 isoseismal by Schermer and others indicates that one of them could have ruptured in the 1934 Pahiatua earthquake.

scholarly journals Active faulting in the Gulf of Aqaba: New knowledge from the MW 7.3 earthquake of 22 November 1995

1999 ◽  
Vol 89 (4) ◽  
pp. 1025-1036 ◽  
Author(s):  
Yann Klinger ◽  
Luis Rivera ◽  
Henri Haessler ◽  
Jean-Christophe Maurin
Keyword(s):  
Body Wave ◽  
Background Level ◽  
Dead Sea ◽  
Strike Slip ◽  
Historical Seismicity ◽  
Global Network ◽  
Arabian Plate ◽  
Gulf Of Aqaba ◽  
African Plate ◽  
Slip Mechanism

Abstract On 22 November 1995 the largest earthquake instrumentally recorded in the area, with magnitude MW 7.3, occurred in the Gulf of Aqaba. The main rupture corresponding to the strike-slip mechanism is located within the gulf of Aqaba, which forms the marine extension of the Levantine fault, also known as the Dead Sea fault. The Levantine fault accommodates the strike-slip movement between the African plate and the Arabian plate. The Gulf of Aqaba itself is usually described as the succession of three deep pull-apart basins, elongated in the N-S direction. Concerning historical seismicity, only two large events have been reported for the last 2000 years, but they are still poorly constrained. The seismicity recorded since installation of regional networks in the early 1980s had been characterized by a low background level punctuated by brief swarmlike activity a few months in duration. Three swarms have already been documented in the Gulf of Aqaba in 1983, 1990, and 1993, with magnitudes reaching at most 6.1 (MW). We suggest that the geometry of the rupture for the 1995 event is related to the spatial distribution of these previous swarms. Body-wave modeling of broadband seismograms from the global network, along with the analysis of the aftershock distribution, allow us to propose a well-constrained model for the rupture process. Northward propagation of the rupture has been found. We have demonstrated that three successive subevents are necessary to obtain a good fit between observed and synthetic wave forms. The total seismic moment released was 7.42 × 1019 N-m. The location of the subsevents shows that the three stages of the rupture involve three different segments within the gulf. Substantial surface breakage showing only normal motion (up to 20 cm) affecting beachrock was observed along the Egyptian coast. We show that these ruptures are only a secondary feature and are in no case primary ruptures. The stress tensor derived from striations collected in quaternary sediments shows radial extension. This result supports landsliding of the beach terraces under the action of the earthquake shaking.

scholarly journals Constraints on Complex Faulting during the 1996 Ston–Slano (Croatia) Earthquake Inferred from the DInSAR, Seismological, and Geological Observations

2020 ◽  
Vol 12 (7) ◽  
pp. 1157 ◽  
Author(s):  
Marin Govorčin ◽  
Marijan Herak ◽  
Bojan Matoš ◽  
Boško Pribičević ◽  
Igor Vlahović
Keyword(s):  
Maximum Stress ◽  
Field Studies ◽  
Fault Rupture ◽  
Stress Release ◽  
Ground Displacement ◽  
Lateral Component ◽  
Fringe Patterns ◽  
The Town ◽  
Additional Constraints ◽  
Complex Faulting

This study, involving remote sensing, seismology, and geology, revealed complex faulting during the mainshock of the Ston–Slano earthquake sequence (5 September, 1996, Mw = 6.0). The observed DInSAR interferogram fringe patterns could not be explained by a single fault rupture. Geological investigations assigned most of the interferogram features either to previously known faults or to those newly determined by field studies. Relocation of hypocentres and reassessment of fault mechanisms provided additional constraints on the evolution of stress release during this sequence. Available data support the scenario that the mainshock started with a reverse rupture with a left-lateral component on the Slano fault 4.5 km ESE of Slano, at the depth of about 11 km. The rupture proceeded unilaterally to the NW with the velocity of about 1.5 km/s for about 11 km, where the maximum stress release occurred. DInSAR interferograms suggest that several faults were activated in the process. The rupture terminated about 20 km away from the epicentre, close to the town of Ston, where the maximum DInSAR ground displacement reached 38 cm. Such a complicated and multiple rupture has never before been documented in the Dinarides. If this proves to be a common occurrence, it can pose problems in defining realistic hazard scenarios, especially in deterministic hazard assessment.

Seismotectonic Snapshots: The 18 March 2020 Mw 5.7 Magna, 31 March 2020 Mw 6.5 Stanley, and 15 May 2020 Mw 6.5 Monte Cristo Intermountain West Earthquakes

2021 ◽  
Author(s):  
Steven G. Wesnousky
Keyword(s):  
Active Faults ◽  
Relative Size ◽  
Fault System ◽  
Intermountain West ◽  
Surface Rupture ◽  
Slip Mechanism ◽  
Walker Lane ◽  
Earthquake Ruptures ◽  
Seismic Networks ◽  
Broad Region

Abstract Seismological characteristics of the 18 March 2020 Mw 5.7 Magna, 31 March 2020 Mw 6.5 Stanley, and 15 May 2020 Mw 6.5 Monte Cristo Intermountain West earthquakes are largely consistent with expectations arising from observations accumulated over the ∼40  yr since implementation and subsequent growth of seismic networks in the broad region. Each occurred within a zone of relatively elevated seismicity, active faults, and geodetically observed strain accumulation. Aftershock distributions in each are confined primarily to depths of <15  km, and the total number of aftershocks correlates with the relative size of the events. In each case, the number per day decays exponentially in the days following the mainshock. None of the mainshocks was preceded by a foreshock sequence that delivered a plausible warning of the impending earthquakes. With respect to tectonics, each earthquake brings new insights. The Stanley and Monte Cristo earthquakes are at the margins of geodetically defined regions of right-lateral transtension, though the pattern of faulting in each region is markedly different. The strike-slip mechanism of the Stanley earthquake stands in contrast to the zone of normal major range bounding faults and historical earthquake ruptures that characterize the region in which it occurred and is the first relatively well instrumented event to show a rupture extending northward through the Trans-Challis fault system. The Magna event has been interpreted to represent low-angle normal slip near the base of a listric Wasatch range bounding fault (Pang et al., 2020). The east-striking left-lateral Monte Cristo earthquake within the Walker Lane is in contrast to the major northwest-striking right-lateral faults that dominate the area, though predictable from prior regional mapping. Surface rupture reportedly accompanied only the Monte Cristo earthquake, though its trace does not clearly follow the zone of aftershocks.

Centrifuge modeling of geotechnical mitigation measures for shallow foundations subjected to reverse faulting

2018 ◽  
Vol 55 (8) ◽  
pp. 1130-1143 ◽  
Author(s):  
Mehdi Ashtiani ◽  
Abbas Ghalandarzadeh ◽  
Mehdi Mahdavi ◽  
Majid Hedayati
Keyword(s):  
Active Faults ◽  
Mitigation Strategies ◽  
Centrifuge Modeling ◽  
Mitigation Measures ◽  
Embedment Depth ◽  
Fault Rupture ◽  
Centrifuge Tests ◽  
Reverse Faulting ◽  
Embedded Foundations ◽  
Dip Angle

Surface fault ruptures are particularly damaging to buildings, lifelines, and bridges located across or adjacent to active faults. These structures should be designed in consideration of surface fault rupture hazards or strategies should be adopted to protect the structures from fault-induced damage. Geotechnical mitigation strategies such as diversion of the fault rupture away from the structure and diffusion of the rupture over a wide zone are possible strategies. The effectiveness of these geotechnical mitigation measures for reverse faulting on shallow embedded foundations was investigated using a series of centrifuge tests. These measures included excavation of a vertical trench adjacent to the foundation and installation of geogrid layers beneath the foundation. The trench was shown to be effective for a range of foundation positions depending on the magnitude of the fault offset, dip angle of the fault, depth of the trench, embedment depth of the foundation, and the number of trenches used. The geogrid layers prevented a distinct fault rupture from reaching the surface and spread fault displacement over a wider zone, but were unable to mitigate the surface fault rupture hazard for shallow embedded foundations.

scholarly journals Analysis of M 5.3 Sumbawa, Indonesia earthquake 2020 and its aftershocks based on hypocenter relocation from BMKG seismic stations

2021 ◽  
Vol 873 (1) ◽  
pp. 012070
Author(s):  
M Ramdhan ◽  
Priyobudi ◽  
A Mursityanto ◽  
K H Palgunadi ◽  
Daryono
Keyword(s):  
Focal Mechanism ◽  
Difference Method ◽  
Fault Plane ◽  
Active Faults ◽  
Disaster Mitigation ◽  
Double Difference ◽  
Seismic Stations ◽  
Hypocenter Relocation ◽  
Splay Faults ◽  
Moderate Magnitude

Abstract The 2020 Sumbawa earthquake of moderate magnitude (M 5.3) produced very significant aftershocks. Based on the computation of Utsu’s method, those aftershocks would be ended after the 20th day. Those earthquakes along 20 days were relocated using double-difference method. The relocation results show the southwest-northeast orientation and getting deeper into the northwest direction. Those two directions show the strike and the dip from the fault plane of the earthquake which was consistent with the focal mechanism released by the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG). Those results showed the majority of earthquakes occurred at a depth of shallower than 20 km. Those earthquake depths were fit with the previous study showing the crustal thickness beneath Sumbawa Island that was about 28 km. We also found that those earthquakes occurred at splay faults propagating to decollement structure. This study is beneficial for earthquake disaster mitigation especially in updating active faults on Sumbawa Island.

scholarly journals Geologic structure of the Taltal Area, Northern Chile, in relation to the earthquake of December 28, 1966

1968 ◽  
Vol 58 (3) ◽  
pp. 835-842 ◽  
Author(s):  
Walter J. Arabasz
Keyword(s):  
Upper Mantle ◽  
Lower Crust ◽  
Active Faults ◽  
Strike Slip ◽  
Northern Chile ◽  
Geologic Structure ◽  
Aftershock Distribution ◽  
Distinctive Features ◽  
Late Mesozoic ◽  
The Town

abstract The Taltal area, which lies within the coastal cordillera of northern Chile, is dominated by a group of major active faults that cut a eugeosynclinal section of predominantly Jurassic andesites overlying Paleozoic metamorphic and plutonic rocks and intruded by Late Mesozoic plutons. The Atacama fault, a suggested regional strike-slip fracture parallel to the coastline, has been obliquely cut and left-laterally offset 10 km by the Taltal fault, which passes through the town of Taltal. Three distinctive features were found to be consistently offset 10 km by the Taltal fault: the easternmost strand of the Atacama fault, an intrusive contact, and a unique volcanic unit. Former continuity of the Atacama fault through the Taltal region is proposed, and subsequent disruption by the Taltal fault appears to have caused major structural readjustments in the still-active Atacama fault zone. The tentative offshore epicenter and aftershock distribution of the December 28 earthquake are not directly correlative with faults that have been mapped in the nearby on-shore areas; this lack of correlation is not surprising in view of the suggested depths of hypocenters in the lower crust or upper mantle.

Active faults, paleoseismology, and historical fault rupture in northern Wairarapa, North Island, New Zealand

2004 ◽  
Vol 47 (1) ◽  
pp. 101-122 ◽  
Author(s):  
E. R. Schermer ◽  
R. Van Dissen ◽  
K. R. Berryman ◽  
H. M. Kelsey ◽  
S. M. Cashman
Keyword(s):  
New Zealand ◽  
Active Faults ◽  
Fault Rupture

Zbąszynek (Neu Bentschen)

Architectura ◽  
2019 ◽  
Vol 47 (1-2) ◽  
pp. 116-131
Author(s):  
Miron Urbaniak
Keyword(s):  
Catholic Church ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Town Hall ◽  
Protestant Church ◽  
The Status ◽  
Railway Workers ◽  
The Town ◽  
Privately Owned

AbstractZbąszynek (Neu Bentschen), a German border post, with accommodation for railway workers, customs officials, postmen and border guards, was established primarily between 1923 and 1930. It was built in the middle of the countryside, designed according to the garden city concept and provided with an urban technical infrastructure. In the years 1932 to 1945, the town had the status of a rural parish. The majority of the houses and civic buildings (railway station, school, town hall, Protestant church, Catholic church, inn) were designed by Wilhelm Beringer from the Deutsche Reichsbahn administration in Frankfurt (Oder). He incorporated neo-baroque and expressionist motifs. The monumental and expressionist water tower, designed by Bruno Möhring from Berlin, is also worth noting. The town comprised two parts. The eastern part contained housing for company workers and officials, a school at the main town square and an inn; the western part was intended – though the idea was short-lived – to comprise privately owned houses, both churches and the town hall. By design, the slaughterhouse, sewage treatment plant and cemetery were all placed on the periphery of the town. The two parts were, and still are divided by ul. Wojska Polskiego, Zbąszynek’s main street. Its southern end is the imposing pl. Dworcowy, the Station Square, taking the form of a cour d’honneur.

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