Conveners
T1.2 e-poster session: e-poster session - T1.2 - The Solid Earth and its Structure
- Gerhard Graham (CTBTO Preparatory Commission, Vienna, Austria)
- Haijun Wang (CTBTO Preparatory Commission, Vienna, Austria)
- Nurcan Meral Ozel (CTBTO Preparatory Commission, Vienna, Austria)
T1.2 e-poster session: T1.2 - The Solid Earth and its Structure
- Gerhard Graham (CTBTO Preparatory Commission, Vienna, Austria)
- Nurcan Meral Ozel (CTBTO Preparatory Commission, Vienna, Austria)
Description
T1.2
Madagascar has never had a big earthquake until now. The biggest earthquake had a magnitude of 7 Richter, and not on land but in the ocean. The highest magnitude on land was below 6 Richter. The central part of the big island is the most active seismically. It can be clustered into three zones. Two of them are a Cenozoic volcanic area, which are Itasy and Ankaratra, from the north-west and the...
Space-temporal distribution of seismic activities in Western and Central Uzbekistan is considered. Four groups of strong earthquakes in the regions were analyzed. The pattern of redistribution of the accumulated tectonic energy in the form of seismic activity in the regions is revealed. In a west-east direction, an increase in the depth of earthquakes is noted. Deviations from the regularity...
Sumatra and West Java have a high potential for geological disasters, including volcanic eruptions and earthquakes. In the last two years BMKG has significantly increased the number of seismic stations in this area, by utilizing seismic waveforms recorded by the BMKG seismograph network of earthquake monitoring stations spread across the Sumatra (110 stations) and West Java (48 stations) for 5...
We analyze foreshock activity in the Iranian plateau by investigating the occurrence patterns for isolated M >= 5.5 earthquakes from 1968 to 2018. Among the 165 mainshocks with M >= 5.5 (after excluding 12 aftershocks, 6 swarms and 9 doublets), 18 percent are preceded by at least one foreshock within 30 days and 20 km. However, the number of events in each foreshock sequence is significantly...
A gravity analysis and Interpretation are carried out using data collected by Sun-Oil Company in the area west of Khartoum between latitudes 15◦ -17◦ N and longitude 30◦-33◦ E. The data released in a Bouguer anomaly map at scale of 1:500,000 and a contour interval of 5mgal.The target is to analyze and interpret the gravity data in terms of surface and subsurface geology. The qualitative...
We investigate seismic attenuation characteristics of the Canadian portion of the northern Appalachians. Coda Q is determined using 389 earthquakes (1.8 =< M =< 3.9) recorded on four stations of the Canadian National Seismic Network (CNSN) in New Brunswick from 1985 to 2020. For comparison, we divide the study area into northern and southern portions, each with two seismic stations and 162 and...
Algeria suffered frequently from effects of destructive moderate sized and strong earthquakes because of the seismotectonic setting on the boundary of African and Eurasian tectonic plates. On May 14th, 2010 at 13 h 29 m GMT, a moderate earthquake of magnitude Md 5.2 (CRAAG – Algeria) struck Beni-Illmane a village located about 200 km southeast of Algiers. The main shock caused substantial...
In this research, a local earthquake magnitude formula (ML and MLv) was developed for measuring earthquake magnitude in northern Thailand and determined station magnitude corrections. By using data from 31 seismic stations of the Earthquake Observation Division, the Thai Meteorological Department and CTBTO Chiang Mai seismic station, analyzed 148 earthquake events from 2009 to 2019 to find the...
Soft soil effectively changes the behaviour of seismic wave propagation and this is important for urban areas. Waveform modelling is one of the methods we can go through site effect and check how the underlying structure could amplify incoming waveform and how will affect low and high rise buildings. In this study, we have monitored a situation with and without soft soil on some existing...
The present work seeks to study the seismic upper mantle discontinuities of the northwestern part of South America and report the results of the first P-to-S radial receiver function investigation of the 410 km and 660 km depth discontinuities that bound the mantle transition zone (MTZ) beneath Colombia. In order to calculate the receiver functions and generate a first-order approximation of...
Calculation of moment tensors of weak seismic events is challenging. Quite often we face a lack of stations and inaccurate velocity models. However information on moment tensors is important for understanding origin of the events (explosions, natural and induced earthquakes) and seismotectonic regime of the area. We re-analyzed two methods of retrieving moment tensors: (i) Inversion of...
Effects of reservoir filling are studied well during past decades by increasing monitoring stations around dams. In this study, a period of more than 10 years of seismicity around Seymareh dam (a major dam Southwestern Iran) is monitored and thousands of minor earthquakes around the lake is processed and evaluated before and after reservoir filling. Various parameters of active locations and...
Instrument response issues are common in seismology, and they can hinder research. We use large data sets to develop models that will predict high-frequency seismic amplitudes, which requires extensive quality control. To identify response and station health issues, we have collected time histories of noise measurements near (but not restricted to) midnight to eliminate diurnal variations, and...
Various type of magnitude scales are recognized for estimating the earthquakes size. Magnitude is one of the significant factors for a unified earthquakes catalog which is needed for seismic hazard assessment and disaster management. The variation in magnitude value from seismological agency to other stimulated the researchers to study the regression relationship between the magnitudes. The...
In this research, the difference between the velocity of Rayleigh and Love waves is used to determine radial anisotropy beneath the Zagros belt. The continuous ambient noise data are processed to image 2D tomographic dispersion maps from the period of 8 to 50 s. Then, a quasi-3D shear wave velocity and radial anisotropy model are calculated by joint inversion of the Rayleigh and Love local...
To advance the understanding of the tectonic processes shaping the African continent, we construct the first continental-scale shear-wave velocity (Vs) model of the lithosphere from the joint analysis of ambient seismic noise and earthquake data recorded by ~1529 seismic stations in and around Africa. We apply the widely used ambient noise cross-correlation and earthquake two-station methods...
Nepal is exposed to intense seismic activity, including devastating earthquakes. The National Earthquake Monitoring and Research Centre (NEMRC) was established under the Department of Mines and Geology (DMG) to monitor those earthquakes. It also alerts the Nepalese authorities and population about the location and magnitude of the felt earthquakes to support rescue and relief operations at the...
Increased urban development, occasional volcanic swarms, and large earthquakes surrounding the Kingdom of Saudi Arabia (KSA) have contributed to a renewed interest in understanding seismic hazard and risk within the Kingdom. In response, the KSA has expanded the national seismic network over the past several decades. Now, a sizable collection of local and regional data provides an...
Although earth fissures have occurred in some parts of the country, they have not been well-documented or studied in detail. Recent field investigation into the formation and extent of earth fissures in Chikwawa District, reveal their formation due to erosion as well as tensional cracks within the affected area as a result of groundwater withdrawal from the alluvial sediments. Several...
On this research we present a probabilistic seismic hazard map for Bolivia (PSHBO-2019), this is the first map that integrated all variables available within the geo hazard for our country. We propose 13 seismic zones based on epicentral distribution, stresses and geology context, we applied the well know method for hazards assessment integration to all variables to have the maximum probable...
Iraq is a country subject to seismic activity associated in a belt Zagros-Taurus which is caused by the collision of the Arab plate with the Eurasian plate. Where the Arab plate is affected by three types of tectonic boundaries: divergent boundaries, convergent boundaries, seam boundaries. The Arab plate moves north-east, leading to the expansion of the area of the Red Sea and the Gulf of Aden...
The postseismic slip that follows large earthquakes is typically a few tens of percent of the coseismic moment, while the postseismic slip following small earthquakes appears to be comparable to the moment. Here I estimate the postseismic slip following intermediate-magnitude earthquakes and find that it is intermediate between the two, about 40% of the coseismic moment. The variation in...
Probabilistic Seismic Hazard Assessment (PSHA) for the state of Uttarakhand (280-320 N and 770-810 E) has been investigated considering two Next Generation Attenuation (NGA) models. Results are presented in terms of PGA for various return periods for each district. Initially, based on seismicity and seismtectonic characteristics the whole region has been defined into four seimogenic zones...
Earthquake disaster mitigation is required to perform in DKI Jakarta which is the Capital of the State of Indonesia. To find out the geological characteristics of the study area such as soil type and rock type, an HVSR analysis was performed. The amplification value and dominant frequency can be used to estimate the level of building damage due to earthquake, damage to buildings due to the...
The present seismological study, focused around Algarve region, was carried out through a cooperation project between the Universities of Évora (Portugal), Lisbon (Portugal), Strasbourg (France) and the IPMA (Lisbon, Portugal). To locate the seismic events and find the local velocity structure of the epicentral area, the P and S arrival times at 38 stations are used (Geostar stations,...
Investigation of the lithospheric shear-wave velocity as a clue helps to improve our understanding of Iranian plateau evolution. Therefore, we estimate shear wave velocity models beneath profiles perpendicular to the Zagros strike by using trans-dimensional Bayesian inversion of the Rayleigh wave group velocity dispersions at periods of 5-120 s. Our velocity models, in line with the support of...
The seismicity change in time in the seismically active region around the central part of the Baikal rift zone (BRZ), the South-East of Russia, was investigated using the statistical estimate of the seismicity level (SESL’09) procedure [Saltykov, 2011]. The method is based on calculating the statistical distribution function of the decimal logarithm of the total seismic energy within a given...
To study the earthquakes and better understand the tectonics in Myanmar, Earth Observatory of Singapore (EOS) has been collaborating with local seismic monitoring authority to install (30) broadband seismic stations. With the broadband collected data, we have used them to study the site classification, earthquakes relocation and constrain the velocity structure.
We defined our EOS’s broadband...
Nigeria lies within the West African sub-region and the country is believed to be aseismic in nature. Despite this view by prominent geoscientists, the country has witnessed both historical and instrumental earthquakes since 1933. The recent recorded chains of events with moment magnitudes ranging from 3.0 to 3.4 in Nigeria, were located in Kaduna state and Abuja. Reasons which include shallow...
Seismic hazard assessment for any region in the world has become a very serious and difficult task for seismologists, civil engineers and decision makers. Probabilistic hazard studies are conducted at the Observatorio San Calixto (PSHBO-2019) to estimate the maximum peak ground acceleration integrating all available variables, however no strong motion time-series (waveform) were applied due to...
On 7 April 2012, a massive snow avalanche occurred in the north-western mountains of Pakistan, close to the Indian and Chinese borders. To mitigate its future hazard, different triggering mechanisms have been investigated in this study. The avalanche signal was clearly recorded on both infrasound and seismic stations, located at varying distances between 300 and 450 km. The avalanche occurred...
UAE strong motion network consists of 62 stations distributed all over the country to construct UAE-Ground GSM “ShakeMaps” for existing urban areas and areas under strategic development. Additionally, structural design parameters will become available for verification and calibration of the seismic design code. Forty stations are equipped with shallow borehole EpiSensors and fourteen stations...
A function of global monitoring of nuclear explosions is the development of Earth models for predicting seismic travel times for more accurate calculation of event locations. Most monitoring agencies rely on fast, distance-dependent one-dimensional (1D) Earth models to calculate seismic event locations quickly and in near real-time. RSTT (Regional Seismic Travel Time) is a seismic velocity...
This research assesses the seismic hazard and deaggregation in the State of Kuwait. For this purpose, the historical and instrumental seismic catalogues of Kuwait and the active Zagros Seismic Belt were compiled, unifying the magnitudes, removing unnecessary earthquakes (seismicity declustering) and considering the completeness of the catalogues. Multi-seismotectonic models for the Kuwait...
In this study, we show results from ambient noise tomography at the KTB drilling site, Germany. The Continental Deep Drilling Project, or ‘Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland’ (KTB) is at the northwestern edge of the Bohemian Massif and is located on the Variscan belt of Europe. During the KTB project crustal rocks have been drilled down to 9 km depth and several...
