scholarly journals Inferring the depth of pre-instrumental earthquakes from macroseismic intensity data: a case-history from Northern Italy

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Paola Sbarra ◽  
Pierfrancesco Burrato ◽  
Patrizia Tosi ◽  
Paola Vannoli ◽  
Valerio De Rubeis ◽  
...  
Keyword(s):  
Focal Depth ◽  
Historical Earthquakes ◽  
Northern Italy ◽  
Macroseismic Intensity ◽  
Intensity Data ◽  
Seismogenic Source ◽  
Seismogenic Faults ◽  
Intensity Field ◽  
Different Depths ◽  
Recent Earthquakes

Abstract Determining the hypocentral depth of pre-instrumental earthquakes is a long-standing geophysical issue that still awaits to be elucidated. Using very well documented recent earthquakes we found that the depth of crustal and upper-mantle events correlates well with the slope of the first 50 km of their intensity attenuation curve, regardless of their magnitude. We used this observation to build a magnitude-independent method for calculating the depth of selected historical and early-instrumental earthquakes of northern Italy based on their macroseismic intensity field. Our method relies on both standard intensity data and questionnaire-based data for 20 earthquakes, encompassing a relatively large range of magnitude (Mw 4.0–5.8) and depth (3.0–72.4 km), that occurred in Northern Italy between 1983 and 2019. We then used the method to estimate the depth of 20 older earthquakes that occurred in the same region between 1570 and 1972. Knowing the approximate depth of historical earthquakes is crucial for assigning them to the relevant seismogenic source, especially where seismogenic faults occur at different depths, allowing for a better characterisation of the region’s seismotectonic setting. Knowing the focal depth also allows recalculating the equivalent magnitude, which turns out to be consistently larger for deeper events, suggesting a reassessment of the local seismic hazard.

Estimates of magnitudes and short-period wave attenuation of Chinese earthquakes from Modified Mercalli intensity data

1984 ◽  
Vol 74 (3) ◽  
pp. 957-968
Author(s):  
Peishan Chen ◽  
Otto W. Nuttli
Keyword(s):  
Wave Attenuation ◽  
Body Wave ◽  
Empirical Relation ◽  
Historical Earthquakes ◽  
The Body ◽  
Intensity Data ◽  
Mountainous Regions ◽  
Short Period ◽  
Recent Earthquakes ◽  
Period Wave

Abstract Intensity data for Chinese earthquakes are used to estimate the body-wave magnitude, mb, of selected historical earthquakes and to estimate Q0, the 1-sec period Q value of Lg waves for various geographical areas of China. In order to derive the necessary empirical relation between the intensity distribution and mb, data are used from recent earthquakes, for which instrumentally obtained mb values as well as isoseismal maps are available. Average Qo values are approximately 175 for the mountainous regions of southwest China, 550 for southeastern China, and 150 for Taiwan. These values agree qualitatively with those obtained by Evernden (1983) and Chen et al. (1983), who utilized a different method of analysis of the intensity data

scholarly journals THE RESIZING OF THE MOST POWERFUL ITALIAN INSTRUMENTAL EARTHQUAKE (SEPTEMBER 8, 1905, CALABRIA REGION, SOUTHERN ITALY)

2021 ◽  
Vol 64 (Vol. 64 (2021)) ◽  
Author(s):  
Luigi Cucci
Keyword(s):  
Seismic Event ◽  
Historical Earthquakes ◽  
The Novel ◽  
Individual Values ◽  
Systematic Revision ◽  
Geological Evidence ◽  
Seismic Catalogue ◽  
A Value ◽  
Seismogenic Source ◽  
Different Depths

The 8 September 1905 Calabria earthquake is the seismic event for which the Italian Seismic Catalogue shows the highest instrumental magnitude of the whole dataset. However, the reported Ms=7.47 was calculated over only two stations, and leaves room for a revision. In this work I provide a new estimate of the surface-wave magnitude of the earthquake calculated over sixteen individual values of magnitude from seven different stations. The new estimate is Ms=7.06±0.13, a value that is consistently lined up with other estimates provided by means of macroseismic or geological evidence. The novel estimate is stable despite alternative epicentral locations and different depths proposed for this event by several investigators. The net variation of almost half a unit magnitude implies a resizing of the seismogenic source of the event in the frame of the seismotectonics of the region, and highlights the strong need for a systematic revision of the instrumental magnitude estimates for several ‘historical’ earthquakes that occurred at the dawning of the instrumental seismology.

scholarly journals Macroseismic intensity data of the 22 April 2013 Tenk (Hungary) earthquake

2014 ◽  
Vol 49 (3) ◽  
pp. 283-294
Author(s):  
Gyöngyvér Szanyi ◽  
Zoltán Gráczer ◽  
Erzsébet Győri
Keyword(s):  
Macroseismic Intensity ◽  
Intensity Data

Contemporary deformation and earthquake hazard of the Capital Circle of China inferred from GPS Measurements

2021 ◽  
Author(s):  
Shaogang Wei ◽  
Xiwei Xu ◽  
Tuo Shen ◽  
Xiaoqiong Lei
Keyword(s):  
High Risk ◽  
Earthquake Hazard ◽  
Historical Earthquakes ◽  
Tectonic Stress ◽  
Middle Part ◽  
Earthquake Hazards ◽  
Seismic Belt ◽  
Fault Plane Solutions ◽  
The North ◽  
Recent Earthquakes

<p>The Capital Circle (CC) is a region with high risk of great damaging earthquake hazards. In our present study, by using a subset of rigorously GPS data around the North China Plain (NCP), med-small recent earthquakes data and focal mechanism of high earthquakes data covering its surrounding regions, the following major conclusions have been reached: (a) Driven by the deformation force associated with both eastward and westward motion, with respect to the NCP, of the rigid South China and the rigid Amurian block, widespread sinistral shear appear over the NCP, which results in clusters of parallel NNE-trending faults with predominant right-lateral strike-slips via bookshelf faulting within the interior of the NCP. (b) Fault plane solutions of recent earthquakes show that tectonic stress field in the NCP demonstrate overwhelming NE-ENE direction of the maximum horizontal principal stress, and that almost all great historical earthquakes in the NCP occurred along the NWW-trending Zhangjiakou-Bohai seismic belt and the NNE-trending Tangshan-Hejian-Cixian seismic belt. Additionally, We propose a simple conceptual model for inter-seismic deformation associated with the Capital Circle, which might suggest that two seismic gaps are located on the middle part of Tangshan-Hejian-Cixian fault seismic belt (Tianjin-Hejian segment) and the northeast part of Tanlu seismic belt (Anqiu segment), and constitute as, in our opinion, high risk areas prone to great earthquakes.</p>

scholarly journals A proposal for a new parametrization of historical intensity data providing a better handling of uncertainties

2014 ◽  
Vol 2 (5) ◽  
pp. 3561-3576
Author(s):  
M. Mucciarelli
Keyword(s):  
Hazard Analysis ◽  
Macroseismic Intensity ◽  
Motion Prediction ◽  
Ground Motion Prediction Equations ◽  
Ground Motion Prediction ◽  
Seismicity Rates ◽  
Seismogenic Faults ◽  
The Moment ◽  
Surface Geology

Abstract. In recent times a great deal of research was aimed to the reduction of uncertainties on Probabilistic Seismic Hazard Analysis (PSHA). Most attention was paid to the role of Ground Motion Prediction Equations (GMPEs), while no studies were devoted to a possible larger source of uncertainties: the historical catalogues of earthquakes. In areas where historical catalogues provide a many centuries long record and surface geology does not permit at the moment to have complete catalogues of seismogenic faults, their use is unavoidable for estimating seismicity rates required for PSHA. Their use is also gaining popularity as an independent tool for the estimation of PSHA (D'Amico and Albarello, 2008) or for their use for validation purposes (Stirling and Petersen, 2006; Mucciarelli et al., 2008). This paper proposes an alternative way for the parametrization of historical macroseismic intensity and then discusses which is the real impact of starting uncertainties in intensities on the final uncertainties on PSHA.

scholarly journals Intensity and isoseismal map of 25th November 2007 Delhi earthquake

MAUSAM ◽  
2021 ◽  
Vol 62 (3) ◽  
pp. 417-424
Author(s):  
RAJESH PRAKASH ◽  
R.K. SINGH ◽  
A.K. SHUKLA ◽  
D. SINGH ◽  
B.S. RANA ◽  
...  
Keyword(s):  
Focal Depth ◽  
Analysis Tool ◽  
Stress Release ◽  
Isoseismal Map ◽  
Intensity Field ◽  
Statistical Analysis Tool ◽  
The Mean ◽  
Local Populace ◽  
Earthquake Effects ◽  
Macroseismic Survey

An earthquake of magnitude ML: 4.3 occurred on 25th November 2007 (2312 UTC) in Delhi with hypocenter at 28.56° N / 77.08° E and focal depth 33.1 km. The epicenter was at about 21 km SW of Delhi University. It was widely felt in and around Delhi and created panic among the local populace. A macroseismic survey was conducted in about ten days starting from 27th November, 2007 at 89 locations covering an area of about 1500 sq. km in Delhi and its neighborhood through a questionnaire. The results of the macroseismic survey allowed establishment of spatial distribution of the earthquake effects in the form of isoseismal map generated using geo-statistical analysis tool of ArcGIS 9.1. The isoseismal map shows that most parts of Delhi region experienced an intensity of V on MMI scale, except on northern most region of Delhi where intensity was found IV. The mean isoseismal radii for the zones V, IV, III and II are 29.13, 57.78, 83.63 and 100.75 km, respectively. The orientation of elongated epicentral track of intensity field shows that the stress release was pronounced along Delhi-Sargodha ridge and earthquake was attributed to activities of this ridge.

scholarly journals A real-time prediction model for macroseismic intensity in China

2020 ◽  
Author(s):  
Xu Weixiao ◽  
Yang Weisong ◽  
Yu Dehu
Keyword(s):  
Intensity Distribution ◽  
Rapid Assessment ◽  
Semimajor Axis ◽  
Focal Depth ◽  
Assessment Method ◽  
Macroseismic Intensity ◽  
Lms Algorithm ◽  
Attenuation Relationship ◽  
Intensity Attenuation ◽  
Isoseismal Lines

Abstract The macroseismic intensity spatial distribution is an important input for most rapid loss modeling and emergency work. Data from a total of 175 earthquakes (Ms ≥ 5.0) in China from 1966 to 2014 were collected, and the rapid assessment method of macroseismic intensity distribution was studied. First, simple relationships among the epicentral intensity, magnitude, and focal depth were established. A greater amount of database is used in this study than that in a previous work (Fu and Liu in Sci R 4(5): 350-354 (1960), Mei in Chin J Geophys 9(1): 1–18 (1960), and Yan et al. in Sci Chin 11: 1050-1058 (1984)), and the studied earthquakes all occurred in the last 50 years, providing more accurate and uniform parameter information. As the seismic intensity-attenuation relationship is traditionally used to estimate the intensity distribution, the macroseismic intensity-attenuation relationship for mainland China was fitted by the earthquake data collected in this region. The deviation of the intensity assessment by the macroseismic intensity-attenuation relationship was examined for 43 earthquakes (Ms ≥ 6.0). In addition, seismic damage emergency assessment work requires the isoseismal lines to be constantly modified according to the updated information. Therefore, an improved ellipse intensity-attenuation model was proposed in this study, completed by the establishment of a semimajor axis and semiminor axis length matrix. Based on the initial value of the length matrix obtained by the regression of historical data and survey data from the site, the least mean squares (LMS) algorithm is used to revise the length matrix. In the end, the practicability of this method is verified by a case study of the Lijiang 7.0 earthquake.

New seismological insights from the analyses of historical and recent earthquakes at Ischia Island (Southern Italy)

2020 ◽  
Author(s):  
Stefano Carlino ◽  
Vincenzo Convertito ◽  
Anna Tramelli ◽  
Vincenzo De Novellis ◽  
Nicola Alessandro Pino
Keyword(s):  
Southern Italy ◽  
Historical Earthquakes ◽  
Maximum Magnitude ◽  
Seismogenic Structure ◽  
Gulf Of Naples ◽  
Tectonic Earthquakes ◽  
Recent Earthquakes ◽  
Peculiar Case ◽  
Island Of Ischia ◽  
Northern Sector

<p>We report here a first comparative analysis between recent and historical earthquakes, occurred in the island of Ischia (Southern Italy), which produced heavy damages and thousands of fatalities. The island of Ischia is located in the Gulf of Naples, and represents a peculiar case of resurgent caldera in which volcano-tectonic earthquakes, with low magnitude, have generated large damages and catastrophic effects, as is the case for the 4 March 1881 (I<sub>max</sub>8-9 MCS) and the 28 July 1883 (I<sub>max</sub>10-11 MCS) events. Both the earthquakes struck the northern area of the island, similarly to the recent 21 August 2017 earthquake. The results allowed us to assess the location, as well as the possible dimension and the related maximum magnitude of the seismogenic structure, located in the northern sector of the island, and responsible of damaging earthquakes. Our results also provide an additional framework to interpret mechanisms leading to earthquakes associated with dynamics of calderas.</p><p> </p>

Sign in / Sign up

Export Citation Format

Share Document