The 12 July 1986 St. Marys, Ohio Earthquake and Recent Seismicity in the Anna, Ohio Seismogenic Zone

1987 ◽  
Vol 59 (2) ◽  
pp. 57-62 ◽  
Author(s):  
Susan Y. Schwartz ◽  
Douglas H. Christensen
Keyword(s):  
Seismic Behavior ◽  
Body Wave ◽  
Strike Slip ◽  
Seismogenic Zone ◽  
Landsat Images ◽  
Nodal Plane ◽  
Epicentral Area ◽  
Felt Area ◽  
The Town ◽  
Body Wave Magnitude

Abstract An earthquake with body wave magnitude 4.5 occurred in the Anna Ohio Seismogenic Zone near the town of St. Marys, Ohio on 12 July 1986. The St. Marys earthquake had a seismic moment of 4.5 × 1022 dyne-cm and a maximum intensity of VI in the epicentral area. It is the largest event to occur in the Anna, Ohio region since the events of 2 March 1937 (total felt area magnitude=4.7) and 9 March 1937 (total felt area magnitude=4.9). The focal mechanism for the St. Marys earthquake indicates a nearly pure strike-slip motion with one nodal plane approximately parallel to the proposed Anna-Champaign Fault and a nearly horizontal p-axis oriented east-northeast. Although the locations of the 1937 events are not well-determined, reports of maximum intensities for the 1937 events near Anna, Ohio indicate that they occurred in a distinctly different location from the St. Marys earthquake. The seismicity in the Anna Seismogenic Zone indicates that much of the seismic activity is concentrated in a northwest to southeast elongate region, extending from Anna, Ohio northwest past Celina, Ohio. This trend parallels the proposed Anna-Champaign Fault as well as lineaments which can be detected on Landsat images, which suggests that this fault may be controlling the seismic behavior in this region.

The Sharpsburg, Kentucky, earthquake 27 July 1980: Main shock parameters and isoseismal maps

1982 ◽  
Vol 72 (1) ◽  
pp. 221-236
Author(s):  
Frederick J. Mauk ◽  
Doug Christensen ◽  
Steve Henry
Keyword(s):  
Body Wave ◽  
P Wave ◽  
Eastern United States ◽  
Slip Vector ◽  
Small Component ◽  
Slip Event ◽  
Felt Area ◽  
Body Wave Magnitude ◽  
Epicentral Region ◽  
Average Body

abstract An earthquake having an average body-wave magnitude of 5.1 occurred on Sunday, 27 July 1980 near Sharpsburg, Kentucky. The earthquake was widely felt throughout the Eastern United States and had a maximum Modified Mercalli intensity of VII in the epicentral region. The total felt area was approximately 673,000 km2. The well-constrained focal mechanism based on 128 P-wave first motions combined with other geological and seismological evidence indicates a fault plane striking N42°E, dipping 50°E with a slip vector 184° of the strike. This is a right-lateral strike-slip event with a small component of thrust. Isoseismal data strongly suggest a northeast-directed rupture. The strike is parallel to the trend of the West Hickman Creek fault zone but 30 km to the east of any known faults.

scholarly journals ‘Conjugate’ coseismic surface faulting related with the 29 December 2020, Mw 6.4, Petrinja earthquake (Sisak-Moslavina, Croatia)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Emanuele Tondi ◽  
Anna Maria Blumetti ◽  
Mišo Čičak ◽  
Pio Di Manna ◽  
Paolo Galli ◽  
...  
Keyword(s):  
Relevant Information ◽  
Strike Slip ◽  
Secondary Effects ◽  
Epicentral Area ◽  
Field Surveys ◽  
Fundamental Information ◽  
Tension Cracks ◽  
Transcurrent Faults ◽  
Conjugate Fault ◽  
Geometry And Kinematics

AbstractWe provide here a first-hand description of the coseismic surface effects caused by the Mw 6.4 Petrinja earthquake that hit central Croatia on 29 December 2020. This was one of the strongest seismic events that occurred in Croatia in the last two centuries. Field surveys in the epicentral area allowed us to observe and map primary coseismic effects, including geometry and kinematics of surface faulting, as well as secondary effects, such as liquefaction, sinkholes and landslides. The resulting dataset consists of homogeneous georeferenced records identifying 222 observation points, each of which contains a minimum of 5 to a maximum of 14 numeric and string fields of relevant information. The earthquake caused surface faulting defining a typical ‘conjugate’ fault pattern characterized by Y and X shears, tension cracks (T fractures), and compression structures (P shears) within a ca. 10 km wide (across strike), NW–SE striking right-lateral strike-slip shear zone (i.e., the Petrinja Fault Zone, PFZ). We believe that the results of the field survey provide fundamental information to improve the interpretation of seismological, GPS and InSAR data of this earthquake. Moreover, the data related to the surface faulting may impact future studies focused on earthquake processes in active strike-slip settings, integrating the estimates of slip amount and distribution in assessing the hazard associated with capable transcurrent faults.

scholarly journals Analysis of the Impact of Fault Mechanism Radiation Patterns on Macroseismic Fields in the Epicentral Area of 1998 and 2004 Krn Mountains Earthquakes (NW Slovenia)

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Andrej Gosar
Keyword(s):  
Site Effects ◽  
Strike Slip ◽  
Radiation Patterns ◽  
Seismogenic Fault ◽  
Active Growth ◽  
Epicentral Area ◽  
Slip Mechanism ◽  
Radiation Amplitude ◽  
The Difference ◽  
The Impact

Two moderate magnitude (Mw = 5.6 and 5.2) earthquakes in Krn Mountains occurred in 1998 and 2004 which had maximum intensity VII-VIII and VI-VII EMS-98, respectively. Comparison of both macroseismic fields showed unexpected differences in the epicentral area which cannot be explained by site effects. Considerably, different distribution of the highest intensities can be noticed with respect to the strike of the seismogenic fault and in some localities even higher intensities have been estimated for the smaller earthquake. Although hypocentres of both earthquakes were only 2 km apart and were located on the same seismogenic Ravne fault, their focal mechanisms showed a slight difference: almost pure dextral strike-slip for the first event and a strike-slip with small reverse component on a steep fault plane for the second one. Seismotectonically the difference is explained as an active growth of the Ravne fault at its NW end. The radiation patterns of both events were studied to explain their possible impact on the observed variations in macroseismic fields and damage distribution. Radiation amplitude lobes were computed for three orthogonal directions: radial P, SV, and SH. The highest intensities of both earthquakes were systematically observed in directions of four (1998) or two (2004) large amplitude lobes in SH component (which corresponds mainly to Love waves), which have significantly different orientation for both events. On the other hand, radial P direction, which is almost purely symmetrical for the strike-slip mechanism of 1998 event, showed for the 2004 event that its small reverse component of movement has resulted in a very pronounced amplitude lobe in SW direction where two settlements are located which expressed higher intensities in the case of the 2004 event with respect to the 1998 one. Although both macroseismic fields are very complex due to influences of multiple earthquakes, retrofitting activity after 1998, site effects, and sparse distribution of settlements, unusual differences in observed intensities can be explained with different radiation patterns.

A teleseismic body-wave analysis of the May 1980 Mammoth Lakes, California, earthquakes

1983 ◽  
Vol 73 (2) ◽  
pp. 419-434
Author(s):  
Jeffery S. Barker ◽  
Charles A. Langston
Keyword(s):  
Body Wave ◽  
Moment Tensor ◽  
Normal Fault ◽  
Strike Slip ◽  
Body Waves ◽  
P Wave ◽  
Moment Tensors ◽  
Double Couple ◽  
The Moment ◽  
Mammoth Lakes

abstract Teleseismic P-wave first motions for the M ≧ 6 earthquakes near Mammoth Lakes, California, are inconsistent with the vertical strike-slip mechanisms determined from local and regional P-wave first motions. Combining these data sets allows three possible mechanisms: a north-striking, east-dipping strike-slip fault; a NE-striking oblique fault; and a NNW-striking normal fault. Inversion of long-period teleseismic P and SH waves for the events of 25 May 1980 (1633 UTC) and 27 May 1980 (1450 UTC) yields moment tensors with large non-double-couple components. The moment tensor for the first event may be decomposed into a major double couple with strike = 18°, dip = 61°, and rake = −15°, and a minor double couple with strike = 303°, dip = 43°, and rake = 224°. A similar decomposition for the last event yields strike = 25°, dip = 65°, rake = −6°, and strike = 312°, dip = 37°, and rake = 232°. Although the inversions were performed on only a few teleseismic body waves, the radiation patterns of the moment tensors are consistent with most of the P-wave first motion polarities at local, regional, and teleseismic distances. The stress axes inferred from the moment tensors are consistent with N65°E extension determined by geodetic measurements by Savage et al. (1981). Seismic moments computed from the moment tensors are 1.87 × 1025 dyne-cm for the 25 May 1980 (1633 UTC) event and 1.03 × 1025 dyne-cm for the 27 May 1980 (1450 UTC) event. The non-double-couple aspect of the moment tensors and the inability to obtain a convergent solution for the 25 May 1980 (1944 UTC) event may indicate that the assumptions of a point source and plane-layered structure implicit in the moment tensor inversion are not entirely valid for the Mammoth Lakes earthquakes.

The sirch (Kerman, Iran) earthquake of 28 July 1981—A field investigation

1982 ◽  
Vol 72 (3) ◽  
pp. 841-861
Author(s):  
Hojjat Adeli
Keyword(s):  
Vertical Displacement ◽  
Field Investigation ◽  
Steel Buildings ◽  
Maximum Width ◽  
Epicentral Area ◽  
Historical Monuments ◽  
Fresh Surface ◽  
The City ◽  
The Town ◽  
Epicentral Region

abstract On 28 July 1981 at 17:22 UTC, the Kerman province of southern Iran was shaken by the largest and the most destructive earthquake in its history. Its surface-wave magnitude was about 7.2. The epicenter of the earthquake was located about 45 km southeast of the city of Kerman, the capital of the Kerman province. The shock killed nearly 3,000 people, left more than 31,000 homeless, and destroyed virtually all buildings in the epicentral region within a radius of 30 km. The hardest hit place was the town of Sirch where about 2,000 people died out of a population of 3,500. Surface fractures were observed in several areas, and the earthquake was apparently associated with a fresh surface normal faulting. The maximum vertical displacement was about 1 m. The maximum width of the fracture was 0.5 m. Also, extensive landsliding and numerous rockfalls were observed within the area of maximum damage. Most houses in the epicentral area are of adobe construction, made of sundried clay brick walls, and heavy domed roofs or vaults with clay or mud mortar. Most casualties were due to the collapse of these adobe buildings. However, the performance of unreinforced or reinforced brick buildings, historical monuments, steel buildings, and other types of structures during the earthquake is also discussed in this paper.

Effects of centroid location on determination of earthquake mechanisms using long-period surface waves

1990 ◽  
Vol 80 (5) ◽  
pp. 1205-1231
Author(s):  
Jiajun Zhang ◽  
Thorne Lay
Keyword(s):  
Surface Wave ◽  
Rayleigh Waves ◽  
Body Wave ◽  
Moment Tensor ◽  
Source Location ◽  
P Wave ◽  
Nodal Plane ◽  
Wave Source ◽  
Long Period

Abstract Determination of shallow earthquake source mechanisms by inversion of long-period (150 to 300 sec) Rayleigh waves requires epicentral locations with greater accuracy than that provided by routine source locations of the National Earthquake Information Center (NEIC) and International Seismological Centre (ISC). The effects of epicentral mislocation on such inversions are examined using synthetic calculations as well as actual data for three large Mexican earthquakes. For Rayleigh waves of 150-sec period, an epicentral mislocation of 30 km introduces observed source spectra phase errors of 0.6 radian for stations at opposing azimuths along the source mislocation vector. This is larger than the 0.5-radian azimuthal variation of the phase spectra at the same period for a thrust fault with 15° dip and 24-km depth. The typical landward mislocation of routinely determined epicenters of shallow subduction zone earthquakes causes source moment tensor inversions of long-period Rayleigh waves to predict larger fault dip than indicated by teleseismic P-wave first-motion data. For dip-slip earthquakes, inversions of long-period Rayleigh waves that use an erroneous source location in the down-dip or along-strike directions of a nodal plane, overestimate the strike, dip, and slip of that nodal plane. Inversions of strike-slip earthquakes that utilize an erroneous location along the strike of a nodal plane overestimate the slip of that nodal plane, causing the second nodal plane to dip incorrectly in the direction opposite to the mislocation vector. The effects of epicentral mislocation for earthquakes with 45° dip-slip fault mechanisms are more severe than for events with other fault mechanisms. Existing earth model propagation corrections do not appear to be sufficiently accurate to routinely determine the optimal surface-wave source location without constraints from body-wave information, unless extensive direct path (R1) data are available or empirical path calibrations are performed. However, independent surface-wave and body-wave solutions can be remarkably consistent when the effects of epicentral mislocation are accounted for. This will allow simultaneous unconstrained body-wave and surface-wave inversions to be performed despite the well known difficulties of extracting the complete moment tensor of shallow sources from fundamental modes.

Sign in / Sign up

Export Citation Format

Share Document