Seismology and Tectonic Setting of the 2002 Molise, Italy, Earthquake

2004 ◽  
Vol 20 (1_suppl) ◽  
pp. 23-37 ◽  
Author(s):  
Gianluca Valensise ◽  
Daniela Pantosti ◽  
Roberto Basili
Keyword(s):  
Southern Italy ◽  
Tectonic Setting ◽  
Historical Earthquakes ◽  
Strike Slip ◽  
Normal Faulting ◽  
Axial Part ◽  
Gargano Promontory ◽  
Populated Region ◽  
East West

Two Mw 5.7 earthquakes struck a sparsely populated region of southern Italy, on October 31 and November 1, triggering a swarm-like sequence that lasted for several days. The earthquakes were caused by pure right-lateral slip between 10 and 24 km depth over a nearly vertical, previously undetected east-west fault. This mechanism is not typical for southern Italy, where normal faulting in the uppermost 12 km of the crust seems to dominate. However, east-west strike-slip faulting is kinematically consistent with the widely documented Apennines extension. The earthquake-causative fault appears to connect the Mattinata fault, a major active strike-slip feature cutting across the Gargano promontory, with east-west structures known beneath the axial part of the Apennines. The 2002 earthquakes thus highlighted a mode of earthquake release that may explain several large yet poorly understood historical earthquakes (e.g., 1361, 1456, 1731, 1930) located between the crest of the Apennines and the Adriatic coastline.

Lake Charles, Louisiana, earthquake of 16 October 1983

1988 ◽  
Vol 78 (4) ◽  
pp. 1463-1474
Author(s):  
Donald A. Stevenson ◽  
James D. Agnew
Keyword(s):  
Gulf Coast ◽  
Normal Fault ◽  
Velocity Model ◽  
Strike Slip ◽  
Crystalline Basement ◽  
P Wave ◽  
Normal Faulting ◽  
Significant Evidence ◽  
Lake Charles ◽  
East West

Abstract On 16 October 1983, at 19:40 (UTC), a magnitude 3.8 earthquake occurred near Lake Charles in southwestern Louisiana. The earthquake was felt over an area of 2600 km2 and had a maximum Modified Mercalli intensity of V. This was the first significant Louisiana Gulf Coast earthquake to be recorded and located by nearby microseismic networks. One possible foreshock and three aftershocks also were recorded and located using a velocity model developed for this study. The focal mechanism of the earthquake was determined based on P-wave first motions from 22 local and regional stations. The solution indicates a predominantly east-west trending, southeast-dipping normal fault with a small strike-slip component. The depth of this event (14+ km) provides the first significant evidence that normal faulting within the crystalline basement may control shallower growth faults along the Gulf Coast.

scholarly journals Seismogenic Structure Orientation and Stress Field of the Gargano Promontory (Southern Italy) From Microseismicity Analysis

2021 ◽  
Vol 9 ◽  
Author(s):  
Simona Miccolis ◽  
Marilena Filippucci ◽  
Salvatore de Lorenzo ◽  
Alberto Frepoli ◽  
Pierpaolo Pierri ◽  
...  
Keyword(s):  
Stress Field ◽  
Southern Italy ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Seismic Network ◽  
Maximum Magnitude ◽  
Fault Plane Solutions ◽  
Seismicity Pattern ◽  
The Past ◽  
Gargano Promontory

Historical seismic catalogs report that the Gargano Promontory (southern Italy) was affected in the past by earthquakes with medium to high estimated magnitude. From the instrumental seismicity, it can be identified that the most energetic Apulian sequence occurred in 1995 with a main shock of MW = 5.2 followed by about 200 aftershocks with a maximum magnitude of 3.7. The most energetic earthquakes of the past are attributed to right-lateral strike-slip faults, while there is evidence that the present-day seismicity occur on thrust or thrust-strike faults. In this article, we show a detailed study on focal mechanisms and stress field obtained by micro-seismicity recorded from April 2013 until the present time in the Gargano Promontory and surrounding regions. Seismic waveforms are collected from the OTRIONS Seismic Network (OSN), from the Italian National Seismic Network (RSN), and integrated with data from the Italian National Accelerometric Network (RAN) in order to provide a robust dataset of earthquake localizations and focal mechanisms. The effect of uncertainties of the velocity model on fault plane solutions (FPS) has been also evaluated indicating the robustness of the results. The computed stress field indicates a deep compressive faulting with maximum horizontal compressive stress, SHmax, trending NW-SE. The seismicity pattern analysis indicates that the whole crust is seismically involved up to a depth of 40 km and indicates the presence of a low-angle seismogenic surface trending SW-NE and dipping SE-NW, similar to the Gargano–Dubrovnik lineament. Shallower events, along the eastern sector of the Mattinata Fault (MF), are W-E dextral strike-slip fault. Therefore, we hypothesized that the seismicity is locally facilitated by preexisting multidirectional fractures, confirmed by the heterogeneity of focal mechanisms, and explained by the different reactivation processes in opposite directions over the time, involving the Mattinata shear zone.

Seismotectonic Analysis of the 2019–2020 Puerto Rico Sequence: The Value of Absolute Earthquake Relocations in Improved Interpretations of Active Tectonics

2021 ◽  
Author(s):  
Copeland W. Cromwell ◽  
Kevin P. Furlong ◽  
Eric A. Bergman ◽  
Harley M. Benz ◽  
Will L. Yeck ◽  
...  
Keyword(s):  
Puerto Rico ◽  
Moment Tensor ◽  
Active Tectonics ◽  
Strike Slip ◽  
Fault System ◽  
Normal Faulting ◽  
Rupture Area ◽  
Extensional Faulting ◽  
Dextral Strike Slip ◽  
East West

Abstract We present a new catalog of calibrated earthquake relocations from the 2019–2020 Puerto Rico earthquake sequence related to the 7 January 2020 Mw 6.4 earthquake that occurred offshore of southwest Puerto Rico at a depth of 15.9 km. Utilizing these relocated earthquakes and associated moment tensor solutions, we can delineate several distinct fault systems that were activated during the sequence and show that the Mw 6.4 mainshock may have resulted from positive changes in Coulomb stress from earlier events. Seismicity and mechanisms define (1) a west–southwest (∼260°) zone of seismicity comprised of largely sinistral strike-slip and oblique-slip earthquakes that mostly occurs later in the sequence and to the west of the mainshock, (2) an area of extensional faulting that includes the mainshock and occurs largely within the mainshock’s rupture area, and (3) an north–northeast (∼30°)-striking zone of seismicity, consisting primarily of dextral strike-slip events that occurs before and following the mainshock and generally above (shallower than) the normal-faulting events. These linear features intersect within the Mw 6.4 mainshock’s fault plane in southwest Puerto Rico. In addition, we show that earthquake relocations for M 4+ normal-faulting events, when traced along their fault planes, daylight along east–west-trending bathymetric features offshore of southwest Puerto Rico. Correlation of these normal-faulting events with bathymetric features suggests an active fault system that may be a contributor to previously uncharacterized seismic hazards in southwest Puerto Rico.

TIMING AND CAUSES OF THE DROWNING AND BACK STEP OF THE APULIA CARBONATE PLATFORM (MONTE SACRO SEQUENCE, GARGANO PROMONTORY, SOUTHERN ITALY)

2019 ◽  
Author(s):  
Katherine Jones ◽  
◽  
Daniel J. Lehrmann ◽  
Michele Morsilli ◽  
Khalid Al-Ramadan ◽  
...  
Keyword(s):  
Southern Italy ◽  
Carbonate Platform ◽  
Gargano Promontory

scholarly journals Stratigraphic and Tectonic Setting of the Liguride Units Cropping Out along the Southeastern Side of the Agri Valley (Southern Apennines, Italy)

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 125
Author(s):  
Giacomo Prosser ◽  
Giuseppe Palladino ◽  
Dario Avagliano ◽  
Francesco Coraggio ◽  
Eleonora Maria Bolla ◽  
...  
Keyword(s):  
Field Survey ◽  
Southern Italy ◽  
Tectonic Setting ◽  
Mediterranean Area ◽  
Fold Belt ◽  
Southern Apennines ◽  
Tectonic Structures ◽  
Subsurface Geology ◽  
Multidisciplinary Study ◽  
Geological Map

This paper shows the main results of a multidisciplinary study performed along the southeastern sector of the Agri Valley in Basilicata (Southern Italy), where Cenozoic units, crucial for constraining the progressive evolution of the Southern Apennine thrust and fold belt and, more in general, the geodynamic evolution of the Mediterranean area are widely exposed. In particular, we aimed at understanding the stratigraphic and tectonic setting of deep-sea, thrust-top Cenozoic units exposed immediately to north of Montemurro, between Costa Molina and Monte dell’Agresto. In the previous works different units, showing similar sedimentological characteristics but uncertain age attribution, have been reported in the study area. In our study, we focussed on the Albidona Formation, pertaining to the Liguride realm, which shows most significant uncertainties regarding the age and the stratigraphic setting. The study was based on a detailed field survey which led to a new geological map of the area. This was supported by new stratigraphic, biostratigraphic and structural analyses. Biostratigraphic analysis provided an age not older than the upper Ypresian and not younger than the early Priabonian. Recognition of marker stratigraphic horizons strongly helped in the understanding of the stratigraphy of the area. The study allowed a complete revision of the stratigraphy of the outcropping Cenozoic units, the recognition of until now unknown tectonic structures and the correlation between surface and subsurface geology.

Geological evidence for strong historical earthquakes in an “aseismic” region: The Pollino case (Southern Italy)

1997 ◽  
Vol 24 (1-4) ◽  
pp. 67-86 ◽  
Author(s):  
Alessandro Maria Michetti ◽  
Luca Ferreli ◽  
Leonello Serva ◽  
Eutizio Vittori
Keyword(s):  
Southern Italy ◽  
Historical Earthquakes ◽  
Geological Evidence
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