Fault parameters and slip distribution of the 1915 Avezzano, Italy, earthquake derived from geodetic observations

1989 ◽  
Vol 79 (3) ◽  
pp. 690-710
Author(s):  
Steven N. Ward ◽  
Gianluca R. Valensise
Keyword(s):  
Geodetic Network ◽  
Normal Fault ◽  
Resolving Power ◽  
South Central ◽  
Surface Displacements ◽  
Fault Parameters ◽  
Best Fitting ◽  
Length Width ◽  
Large Earthquakes ◽  
Fault Length

Abstract This paper analyzes static surface displacements associated with the Avezzano, Italy, earthquake (Ms = 6.9) of 13 January 1915. The Avezzano event locates on a shallow normal fault centered in the Apennine mountains near a Quaternary tectonic depression named “Conca del Fucino.” The 1915 earthquake is the only sizable event to have occurred in the area for at least a millennium, although many Holocene and Quaternary faults can be recognized in the field. Awareness of the seismic potential of the Fucino region has heightened in recent years with the outward expansion of metropolitan Rome (80 km southwest). Because of a fortuitous pre-earthquake leveling survey near the fault in the mid 19th century, good quality geodetic data exist that illuminate details of the 1915 rupture. We modeled the faulting using both uniform (USP) and variable (VSP) slip planar dislocations. The best fitting focal mechanism includes pure dip slip on a plane striking 135° and plunging 63° to the southwest. This fault geometry is consistent with surface scarps and the broad scale tectonics of the region and is common to several large earthquakes of the south-central Apennines. The USP analysis estimates fault length, width, slip and moment to be 24 km, 15 km, 83 cm, and 9.7 × 1018 N-m, respectively. Numerical simulations indicate that residuals left in the uniform slip model are not entirely random and represent systematically unmodeled features of fault slip. VSP models of the earthquake significantly reduce the USP variance and reveal a broad two-lobed slip pattern, separating a central region of low moment release. New formulations detailing the relationships between VSP and minimum model norm solutions to underdetermined inverse problems are presented as well as concise statements dealing with the intrinsic and combined resolving power of a geodetic network.

scholarly journals Past earthquake timing and magnitude along the Inglewood fault, Taranaki, New Zealand

1994 ◽  
Vol 27 (2) ◽  
pp. 155-162 ◽  
Author(s):  
A. G. Hull
Keyword(s):  
Volcanic Ash ◽  
Surface Displacement ◽  
Normal Fault ◽  
Historical Earthquakes ◽  
Normal Faults ◽  
Single Event ◽  
Ground Shaking ◽  
Large Earthquakes ◽  
Fault Length ◽  
Strong Ground

Several active normal faults in the onshore and offshore regions of Taranaki are capable of generating large earthquakes and associated strong ground shaking. Historical earthquakes are concentrated offshore of Cape Egmont, and no significant earthquakes have been detected along the major onshore surface faults. The northeaststriking Inglewood fault is a major onshore, southward-dipping normal fault. It has a known length of c. 20 km and an average scarp height of c. 3 m on landforms less than about 15,000 yrs old. Three subsurface excavations at two sites along the Inglewood fault about 15 km from New Plymouth have revealed three surface fault displacements during the last c. 13,000 years. Earthquakes resulting in about 1.2 m of surface displacement occurred at c. 3,500 radiocarbon yrs BP; between 4,000 and 9,000 radiocarbon yrs BP; and between 10,000 and 13,000 radiocarbon yrs BP, judged by the amount of vertical offset of dated volcanic ash layers. Based on average single-event fault slip values of 1.2-3.0 m and a fault length of 20-30 km, the estimated earthquake magnitudes associated with these past movements range from Mw 6.7 to 7.2.

Relaxation of the south flank after the 7.2-magnitude Kalapana earthquake, Kilauea Volcano, Hawaii

1994 ◽  
Vol 84 (1) ◽  
pp. 133-141
Author(s):  
John J. Dvorak ◽  
Fred W. Klein ◽  
Donald A. Swanson
Keyword(s):  
Rift Zone ◽  
Vertical Surface ◽  
Kilauea Volcano ◽  
Adjacent Segment ◽  
The South ◽  
Surface Displacements ◽  
Kīlauea Volcano ◽  
Parkfield Earthquake ◽  
Largest Aftershock ◽  
Large Earthquakes

Abstract An M = 7.2 earthquake on 29 November 1975 caused the south flank of Kilauea Volcano, Hawaii, to move seaward several meters: a catastrophic release of compression of the south flank caused by earlier injections of magma into the adjacent segment of a rift zone. The focal mechanisms of the mainshock, the largest foreshock, and the largest aftershock suggest seaward movement of the upper block. The rate of aftershocks decreased in a familiar hyperbolic decay, reaching the pre-1975 rate of seismicity by the mid-1980s. Repeated rift-zone intrusions and eruptions after 1975, which occurred within 25 km of the summit area, compressed the adjacent portion of the south flank, apparently masking continued seaward displacement of the south flank. This is evident along a trilateration line that continued to extend, suggesting seaward displacement, immediately after the M = 7.2 earthquake, but then was compressed during a series of intrusions and eruptions that began in September 1977. Farther to the east, trilateration measurements show that the portion of the south flank above the aftershock zone, but beyond the area of compression caused by the rift-zone intrusions and eruptions, continued to move seaward at a decreasing rate until the mid-1980s, mimicking the decay in aftershock rate. Along the same portion of the south flank, the pattern of vertical surface displacements can be explained by continued seaward movement of the south flank and development of two eruptive fissures along the east rift zone, each of which extended from a depth of ∼3 km to the surface. The aftershock rate and continued seaward movement of the south flank are reminiscent of crustal response to other large earthquakes, such as the 1966 M = 6 Parkfield earthquake and the 1983 M = 6.5 Coalinga earthquake.

Crustal structure in the southern Bering Shelf and the Alaska Peninsula from inversion of surface-wave dispersion data

1989 ◽  
Vol 79 (6) ◽  
pp. 1883-1893
Author(s):  
Mansour Niazi ◽  
Kin-Yip Chun
Keyword(s):  
Crustal Structure ◽  
Velocity Structure ◽  
Structural Characteristics ◽  
Resolving Power ◽  
Surface Wave Dispersion ◽  
Bristol Bay ◽  
Alaska Peninsula ◽  
South Central ◽  
Bering Shelf ◽  
Group Velocities

Abstract Dispersion of surface waves in the southern Bering Shelf (Bristol Bay) and the Alaska Peninsula is investigated for a study of the regional crustal structure. Our data consist of five shallow earthquakes located along the Aleutian Arc and recorded by long-period, three-component seismographs sited in south-central Alaska. Both Love and Rayleigh group velocities are obtained through the application of the phase-matched filtering technique. The results are converted to equivalent pure-path data by appropriate adjustment using the published information for the continental Alaska. Treating the shear velocity of each layer as an independent parameter, the pure-path group velocities of Love and Rayleigh waves are jointly inverted in order to obtain a satisfactory agreement between the theoretical and the observed dispersion characteristics. Estimates of the resolving power of the inversion and uncertainty of the final velocity structure show substantial improvement over the previously published models. With their crustal thicknesses ranging between 33 and 36 km, none of the final models displays structural characteristics reminiscent of an oceanic crust. Over the northernmost path across the Bristol Bay, we found an indication of a weak low-velocity zone (five per cent reduction relative to the lid velocity) whose prominence diminishes towards the south.

Evolution of the south-central segment of the Archean Abitibi Belt, Quebec. Part II: Tectonic evolution and geomechanical model

1983 ◽  
Vol 20 (9) ◽  
pp. 1355-1373 ◽  
Author(s):  
Erich Dimroth ◽  
Lazlo Imreh ◽  
Normand Goulet ◽  
Michel Rocheleau
Keyword(s):  
Tectonic Evolution ◽  
Anisotropic Plate ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Normal Fault ◽  
Geomechanical Model ◽  
Southwestern Part ◽  
South Central ◽  
Central Segment ◽  
Volcanic Terrain

In this paper, we describe the relations between the paleogeographic and tectonic evolution of the southwestern part of the Archean Abitibi and Bellecombe belts. Volcanism in the Abitibi Belt created a very thick, anisotropic plate composed of competent volcanic rocks and broken by the Duparquet–Destor break. The depocenters of the upper division of diverse volcanic rocks subsided about 10 km relative to their surroundings, and some central volcanic complexes within this division were consolidated by synvolcanic plutons and their thermal metamorphic aureole. The Cadillac break, a normal fault, separated the Abitibi and Bellecombe belts. The latter consisted of comparatively incompetent sedimentary rocks on top of a basement composed of ultramafic–mafic flows.North–south compression of the volcanic terrain during the Kenoran Orogeny produced a set of flexure folds, F1, that curve around the consolidated cores of central volcanic complexes generally in an easterly direction. Synclinoria nucleated at the deeply subsident depocenters of the upper diverse division. Further north–south flattening and subvertical stretching produced the east-trending F2 folds, their axial-plane schistosity S2, and local superposed schistosities S3 and S4. Southward verging recumbent folds suggest that the Bellecombe Belt simultaneously was pulled northward below the Abitibi Belt. During the orogeny, the Duparquet–Destor and Cadillac breaks were transformed to thrust faults; the Duparquet–Destor break also shows minor (< 3 km) right-lateral strike slip. Diapiric rise of late- to post-kinematic plutons locally distorted earlier schistosities.

scholarly journals River profile response to normal fault growth and linkage: An example from the Hellenic forearc of south-central Crete, Greece

2016 ◽  
Author(s):  
Sean F. Gallen ◽  
Karl W. Wegmann
Keyword(s):  
Drainage Basin ◽  
Profile Analysis ◽  
Normal Fault ◽  
Drainage Area ◽  
Fault System ◽  
Stream Power ◽  
River Incision ◽  
South Central ◽  
History Of ◽  
Fault Growth

Abstract. Topography is a reflection of the tectonic and geodynamic processes that act to uplift the Earth's surface and the erosional processes that work to return it to base level. Numerous studies have shown that topography is a sensitive recorder or tectonic signals. A quasi-physical understanding of the relationship between river incision and rock uplift has made the analysis of fluvial topography a popular technique for deciphering relative, and some argue absolute, histories of rock uplift. Here we present results from a study of the fluvial topography from south-central Crete demonstrating that river longitudinal profiles indeed record the relative history of uplift, but several other processes make it difficult to recover quantitative uplift histories. Prior research demonstrates that the south-central coastline of Crete is bound by a large (~100 km long) E-W striking composite normal fault system. Marine terraces reveal that it is uplifting between 0.1–1.0 mm yr−1. These studies suggest that two normal fault systems, the offshore Ptolemy and onshore South-Central Crete faults linked together in the recent geologic past (Ca. 0.4–1 Myrs bp). Fault mechanics predicts that when adjacent faults link into a single fault the uplift rate in the linkage zone will increase rapidly. Using river profile analysis we show that rivers in south-central Crete record the relative uplift history of fault growth and linkage, as theory predicts that they should. Calibration of the commonly used stream power incision model shows that the slope exponent, n, is ~ 0.5, contrary to most studies that find n ≥ 1. Analysis of fluvial knickpoints shows that migration distances are not proportional to upstream contributing drainage area, as predicted by the stream power incision model. Maps of the transformed stream distance variable, χ, indicate that drainage basin instability, drainage divide migration and river capture events complicate river profile analysis in south-central Crete. Waterfalls are observed in southern Crete and appear to operate under less efficient and different incision mechanics than assumed by the stream power incision model. Drainage area exchange and waterfall formation are argued to obscure linkages between empirically derived metrics and quasi-physical descriptions of river incision, making is difficult to quantitatively interpret rock uplift histories from river profiles in this setting. Karst hydrology, break down of assumed drainage area-discharge scaling and chemical weathering might also contribute to the failure of the stream power incision model to adequately predict the behavior of the fluvial system in south-central Crete.

scholarly journals Focal mechanism and depth of the 1956 Amorgos twin earthquakes from waveform matching of analogue seismograms

2013 ◽  
Vol 5 (2) ◽  
pp. 1901-1940
Author(s):  
A. Brüstle ◽  
W. Friederich ◽  
T. Meier ◽  
C. Gross
Keyword(s):  
Focal Mechanism ◽  
Transfer Functions ◽  
Body Wave ◽  
Normal Fault ◽  
Benioff Zone ◽  
Grid Search ◽  
African Plate ◽  
Technical Problems ◽  
Time Frequency ◽  
Best Fitting

Abstract. Historic analogue seismograms of the large 1956 Amorgos twin earthquakes which occurred in the volcanic arc of the Hellenic Subduction Zone (HSZ) were collected, digitized and reanalyzed to obtain refined estimates of their depth and focal mechanism. In total, 80 records of the events from 29 European stations were collected and, if possible, digitized. In addition, bulletins were searched for instrument parameters required to calculate transfer functions for instrument correction. A grid search based on matching the digitized historic waveforms to complete synthetic seismograms was then carried out to infer optimal estimates for depth and focal mechanism. Owing to incomplete or unreliable information on instrument parameters and frequently occurring technical problems during recording such as writing needles jumping off mechanical recording systems, much less seismograms than collected proved suitable for waveform matching. For the first earthquake, only 7 seismograms from three different stations (STU, GTT, COP) could be used. Nevertheless, the grid search produces stable optimal values for both source depth and focal mechanism. Our results indicate a shallow hypocenter at about 25 km depth. The best-fitting focal mechanism is a SW–NE-trending normal fault dipping either by 30° towards SE or 60° towards NW. This finding is consistent with the local structure of the Santorini–Amorgos graben. For the second earthquake, 4 seismograms from three different stations (JEN, GTT, COP) proved suitable for waveform matching. Whereas it was impossible to obtain meaningful results for the focal mechanism owing to surface wave coda of the first event overlapping body wave phases of the second event, waveform matching and time-frequency analysis point to a considerably deeper hypocenter located within the Wadati–Benioff-zone of the subducting African plate at about 120–160 km depth.

Age, growth, and condition of the Mud River crayfish Orconectes ronaldi Taylor 2000 (Decapoda: Cambaridae)

2015 ◽  
Vol 21 (1) ◽  
pp. 115-121
Author(s):  
Hannah Noss ◽  
Wendy Anderson ◽  
Thomas P. Simon
Keyword(s):  
Statistical Difference ◽  
Sexually Dimorphic ◽  
Allometric Growth ◽  
Native Range ◽  
South Central ◽  
Length Width ◽  
Wet Weight ◽  
Native Crayfish ◽  
Sexually Mature ◽  
Crayfish Species

Abstract The Mud River crayfish, Orconectes ronaldi Taylor, is a native crayfish species found in the Midwestern United States in Kentucky and Indiana. Length-weight relationship, body morphometric relationship, and condition within the species native range in south-central Indiana were studied. Growth, size relationships based on gender, sexual phase for adults and juveniles and chelae-length/width relationships were used to interpret patterns in sexual dimorphism. Carapace length (CL)–wet weight (Wwt) relationships for all genders (i.e., male, female, juvenile) and all male forms (form I and II) had positive allometric growth. Male individuals were not significantly heavier than females of the same length. The maximum length and weights of males (35.1 mm CL) were longer and heavier (11.8 g) than the longest female (31.5 mm) weighing 8.3 g. No statistical difference in mean weight was observed; however, this is attributed to the accelerated development of the chelae in sexually mature form I males, whereas chelae of females grow slower throughout life. Chelae length was significantly different between male form II and male form I, and male form II and females (P = 0.004, and P <0.001, respectively). The relatively longer chelae of form I and form II males are due to sexually dimorphic change.

scholarly journals Reawakening of large earthquakes in south central Chile: The 2016 M w 7.6 Chiloé event

2017 ◽  
Vol 44 (13) ◽  
pp. 6633-6640 ◽  
Author(s):  
S. Ruiz ◽  
M. Moreno ◽  
D. Melnick ◽  
F. del Campo ◽  
P. Poli ◽  
...  
Keyword(s):  
Central Chile ◽  
South Central ◽  
Large Earthquakes

scholarly journals Measurements of Mixed-Mode Crack Surface Displacements and Comparison With Theory

1980 ◽  
Vol 47 (3) ◽  
pp. 557-562 ◽  
Author(s):  
W. N. Sharpe ◽  
N. J. Altiero ◽  
A. Mirmohamadsadegh
Keyword(s):  
Crack Surface ◽  
Integral Equation Method ◽  
Boundary Integral ◽  
Width Ratio ◽  
Finite Width ◽  
Tension Specimen ◽  
Surface Displacements ◽  
Load Axis ◽  
Sharp Crack ◽  
Length Width

The problem of a finite-width tension specimen containing a crack oriented at various angles to the load axis is attacked from experimental and theoretical viewpoints. Displacements of an electro-machined slot, 12.5 mm long and oriented at angles of 0°, 15°, 30°, 45°, 60°, and 75°, are measured using a laser-based in-plane measuring technique. Various width specimens, ranging from a crack-length/width ratio of 0.167 to 0.794, are tested. A boundary-integral equation method is extended to deal with the presence of a sharp crack. Agreement between the two approaches is generally good except near the tips of the cracks.

scholarly journals River profile response to normal fault growth and linkage: an example from the Hellenic forearc of south-central Crete, Greece

2017 ◽  
Vol 5 (1) ◽  
pp. 161-186 ◽  
Author(s):  
Sean F. Gallen ◽  
Karl W. Wegmann
Keyword(s):  
Profile Analysis ◽  
Normal Fault ◽  
Drainage Area ◽  
Uplift Rate ◽  
Stream Power ◽  
River Incision ◽  
South Central ◽  
History Of ◽  
River Profiles ◽  
Fault Growth

Abstract. Topography is a reflection of the tectonic and geodynamic processes that act to uplift the Earth's surface and the erosional processes that work to return it to base level. Numerous studies have shown that topography is a sensitive recorder of tectonic signals. A quasi-physical understanding of the relationship between river incision and rock uplift has made the analysis of fluvial topography a popular technique for deciphering relative, and some argue absolute, histories of rock uplift. Here we present results from a study of the fluvial topography from south-central Crete, demonstrating that river longitudinal profiles indeed record the relative history of uplift, but several other processes make it difficult to recover quantitative uplift histories. Prior research demonstrates that the south-central coastline of Crete is bound by a large ( ∼  100 km long) E–W striking composite normal fault system. Marine terraces reveal that it is uplifting between 0.1 and 1.0 mm yr−1. These studies suggest that two normal fault systems, the offshore Ptolemy and onshore South-Central Crete faults, linked together in the recent geologic past (ca. 0.4–1 My BP). Fault mechanics predict that when adjacent faults link into a single fault the uplift rate in footwalls of the linkage zone will increase rapidly. We use this natural experiment to assess the response of river profiles to a temporal jump in uplift rate and to assess the applicability of the stream power incision model to this setting. Using river profile analysis we show that rivers in south-central Crete record the relative uplift history of fault growth and linkage as theory predicts that they should. Calibration of the commonly used stream power incision model shows that the slope exponent, n, is  ∼  0.5, contrary to most studies that find n  ≥  1. Analysis of fluvial knickpoints shows that migration distances are not proportional to upstream contributing drainage area, as predicted by the stream power incision model. Maps of the transformed stream distance variable, χ, indicate that drainage basin instability, drainage divide migration, and river capture events complicate river profile analysis in south-central Crete. Waterfalls are observed in southern Crete and appear to operate under less efficient and different incision mechanics than assumed by the stream power incision model. Drainage area exchange and waterfall formation are argued to obscure linkages between empirically derived metrics and quasi-physical descriptions of river incision, making it difficult to quantitatively interpret rock uplift histories from river profiles in this setting. Karst hydrology, break down of assumed drainage area discharge scaling, and chemical weathering might also contribute to the failure of the stream power incision model to adequately predict the behavior of the fluvial system in south-central Crete.

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