Major Earthquakes Of Magnitude Research Articles

The impact of Kahramanmaraş (2023) earthquakes: A comparative case study for Adıyaman and Malatya

This study examines the effects of two major earthquakes of magnitude 7.7 and 7.6 that struck Kahramanmaraş on February 6th, 2023, followed by a magnitude 6.4 quake in Hatay on February 20th, which caused major damage in 11 Turkish provinces. The study focuses on Adıyaman and Malatya and uses an interdisciplinary approach to analyze the economic and environmental impacts. Primary data sources, including field visits and interviews, reveal clear labor-related challenges in both provinces, characterized by a government-induced labor shortage. In both provinces, physical capital has been severely damaged, particularly affecting small businesses, historic bazaars, and old industrial areas. The impact on businesses varies by size and location, with Adıyaman suffering more severe setbacks than other cities. The shortage of skilled labor related to the earthquake damage affects the quality of production, which can have a serious economic impact. Transportation disruptions continue to hamper supply chains and affect companies' ability to meet their export commitments. The environmental consequences, particularly the large amount of debris, pose a major challenge. The lack of a comprehensive disaster waste plan at the central government level leads to inadequate waste management. The study recommends sorting the debris at temporary sites to obtain reusable items while paying attention to the sustainability and transparency of debris management processes. In summary, this comparative case study highlights the need for tailored approaches to address the different impacts in the 11 provinces. A one-size-fits-all solution is insufficient and an individual needs assessment is needed for each province in order to implement targeted economic and environmental recovery measures.

An Optimization of Using the M8 Algorithm for Prediction of Major M7.0+ Earthquakes in the Iranian Plateau

The casualties and financial losses caused by large earthquakes have led to an awareness of prediction importance of such earthquakes. The earthquake prediction is divided into four categories: long term, intermediate term, short term, and immediate. The M8 algorithm is one of the intermediate-term middle-range prediction algorithms primarily used to predict earthquake of magnitude 8 or more and is applied later for smaller magnitudes. The Iranian Plateau is less exposed to earthquake with magnitude 8 or more and it is observed that the seismicity rate in this region is generally low. Thus; the original M8 is not suitable for applying in this region. The objective of this study is to modify the M8 algorithm for Prediction of Major M7.0+ Earthquakes in the Iranian Plateau. The major earthquake of magnitude 7 or more in the Iranian plateau from 1975 to 2018 is considered as the target earthquakes. The hit rate times 1 minus alarm rate is defined as objective function and the particles swarm optimization meta-heuristic algorithm is used to maximize it. The optimum M8 could predict 14 out of 17 large earthquakes in the Iranian plateau while occupying 31.7% of the spatio-temporal space as the alarm. The results show that by employing an optimization algorithm, we can modify the M8 algorithm for efficient prediction of the target magnitudes less than 8 in the regions with low seismicity rate.

Ionospheric perturbations due to earthquakes as determined from VLF and GPS-TEC data analysis at Agra, India

Employing SoftPAL receiver, amplitude variations of VLF transmitter signals NWC (19.8 kHz) and NPM (21.4 kHz) are analyzed at Agra station in India (Geograph. lat. 27.2°N, long. 78°E) ±15 days from five major earthquakes of magnitude M = 6.9–8.5 occurred in Indian subcontinent during the years 2011–2013. We apply nighttime fluctuation (NF) method and show that in almost all cases the trend decreases and dispersion and NF increase on the same days corresponding to each earthquake about 11–15 days prior to the main shock. Assuming that the ionospheric perturbations are caused by atmospheric gravity waves (AGW), we also calculate AGW modulation index for each case and find its values increased on the days amplitude fluctuations take place. Its value is decreased in one case only where the perturbations may be attributed to penetration of seismogenic electric field.In order to support the above results we also present GPS-TEC data analyzed by us corresponding to three of the above earthquakes. We study the TEC anomalies (unusual enhancements) and find that in one case the precursory period is almost the same as that found in NF method.

Lessons learned from the Nepal earthquake 2015

Nepal is one of the most earthquake-prone regions in the world as it lies at the boundary of the actively converging Indo-Australian plate and Eurasian Plate. Most of the infrastructures in Nepal were constructed by individuals based on their own needs and budget without consulting engineers, and several studies have shown that many of these structures are likely to be inadequate in resisting earthquake forces. Though an earthquake design code is present in Nepal, it is not mandatory in every part of the country and people do not follow it properly even where it is mandatory. This paper presents a summary of the reconnaissance survey of a major earthquake of magnitude 7.8 (on 25th of April 2015) with epicentre in Gorkha District in Nepal, followed by a series of aftershocks including magnitude of 7.3 on the 12th of May 2015. This has resulted in 8969 casualties to date and about 900,000 houses and temples were damaged (partially and completely) leaving thousands of people homeless. Problems associated with the current practices in Nepal are discussed in detail and some suggestions are made for improvements in design and construction. Some of the major problems highlighted in the paper include code compliance, quality control in construction, and lack of preparedness.

Spine surgery in Nepal: the 2015 earthquake.

At noon on Saturday, 25 April 2015, a 7.8 magnitude earthquake struck Nepal. It was centered in the Himalaya northwest of Kathmandu, the capital of over 1 million people. The violent tremors were felt as far away as New Delhi, India 1,000 km from the epicenter, but the worst of its destructive force was experienced in the heavily populated Kathmandu valley and in the remote mountainous villages of the Himalaya. Ancient temples crumbled; poorly constructed buildings collapsed; men, women, and children were trapped and injured, sometimes fatally. Avalanches killed mountain climbers, Sherpa guides, and porters at Everest base camp (EBC). The death toll to date exceeds 8,600 with as many as 20,000 injured. Spinal Health International (SHI), a nonprofit volunteer organization, has been active in Nepal in past years and responded to requests by Nepali spine surgeons for assistance with traumatic spine injury victims following the earthquake. SHI volunteers were present during the 2(nd) major earthquake of magnitude 7.3 on 12 May 2015. Past and current experiences in Nepal will be presented.

Is tidal forcing critical to trigger large Sumatra earthquakes?

Complexity in the earthquake mechanism is manifested in different forms such as fractal distribution, clustering of seismicity, etc., and characterized as critical phenomenon. Occurrences of earthquakes generally represent the state of metastable equilibrium. The Andaman–Sumatra subduction zone is one of the most seismically active corridors (possibly in metastable state) in the world. Recently, the region faced three major earthquakes of magnitude more than 8.5 (M ~ 9.1 on December 26, 2004; M ~ 8.6 on March 28, 2005; M ~ 8.6 on April 11, 2012). Researchers have suggested multiple causes of earthquake generation in this region including the one with possible correlation of tidal stresses with earthquake occurrences. The latter issue, however, has been hotly debated in view of the fact that a small stress generated due to tidal forcing cannot cause such a bigger magnitude earthquake. We study here the impact of tidal forcing on critically generated earthquake phenomena. We examined the statistical behavior of recurrence time interval of earthquakes using the available data for period of about 40 years from 1973 to 2013. We constrain the simple empirical toy model using the concept of catastrophe theory to evaluate the impact of small tidal forcing on the critical state of earthquakes occurrences. In addition to the major role of Helmholtz free energy during the plate motion, our analysis suggests that the stability and critical behavior of the earthquake in Sumatra region could be associated with tidal forcing, however, only for triggering of some of the “Catastrophic–Chaotic” earthquake phenomenon.

Effect of the 2004 Mid Niigata Prefecture earthquake on glycemic control in type 1 diabetic patients

At 5:56 p.m. on October 23, 2004, a major earthquake of magnitude 6.8 on the Richter scale struck the Chuetsu district of Niigata Prefecture, Japan, a rural area with mountain villages. Strong aftershocks of grade 5–6 on the Japanese Intensity Scale continued for 2 months. We investigated changes in the HbA1c levels of 65 type 1 diabetic patients with insulin therapy before and throughout the 12 months of aftershocks that followed the earthquake. All patients received insulin therapy via pens with replaceable cartridges or continuous subcutaneous insulin infusion (CSII). Most patients needed four daily insulin injections with rapid- and long-acting insulins. Nineteen percent of patients had the CSII therapy using rapid-acting insulin. The mean HbA1c level in all patients increased significantly ( P < 0.01) from 6.7 ± 0.9% to 7.0 ± 1.0% in the third month, peaked at the fifth month, and decreased at 12 months. Sixty percent of the patients stayed in their own houses after the initial shock, while 40% of patients moved into other houses. Seventeen percent of the patients had severely destroyed houses. The median PTSD score was low in all patients. Within 1 month after the earthquake, the pens with replaceable cartridges were discontinued and disposable pens with prefilled insulin cartridges were used. The incidence of nephropathy increased by 7% by the third month and returned to the pre-earthquake level by the sixth month. Over the 12-month observation period, no other micro- or macro-vascular diseases were newly diagnosed. One patient had transient severe acute hyperglycemia and one needed hemodialysis. However, none of the patients had ketoacidosis, and no other clinical manifestations of disease were noted. In conclusion, it is essential that neighboring organizations respond quickly with sufficient medical support for diabetic patients with insulin therapy following an earthquake. In particular, treatment with rapid- and long-acting insulin injections via disposable pens with prefilled insulin cartridges or CSII therapy is useful during a disaster. To take the medical support, patients should always have a note or copy of their medical records, including medical history and medications used.

Recorded and Numerical Strong Motion Response of a Base-Isolated Bridge

Since 1983, 12 Icelandic bridges have been base isolated for seismic protection. Lead-rubber bearings have been used in all the cases. The Thjorsa River Bridge, built in 1950 and retrofitted with base isolation in 1991, is instrumented by strong-motion accelerometers. The bridge has one 83-m-long main span and two 12-m-long approach spans. Only the main span, a steel arch truss with concrete deck, is base isolated. In June 2000, two major earthquakes of magnitude 6.6 and 6.5 occurred in South Iceland; the epicenter was close to the Thjorsa River Bridge. In the first earthquake, a peak ground acceleration of 0.53 g was recorded at the bridge site, and in the second earthquake, a peak ground acceleration of 0.84 g was recorded. The Thjorsa River Bridge survived the earthquakes without any serious damage and was open for traffic immediately after the earthquakes.

Site amplification in lava rock on soft sediments

Seismicity and volcanic activity in Iceland are related to the Mid-Atlantic plate boundary that crosses the island. Due to volcanic activity, different sea levels through the ages and glacial drift, the geology in Iceland is quite complex at many sites. In June 2000, two major earthquakes of magnitude 6.6 ( M w) and 6.5 ( M w) occurred in southern Iceland. Ground motion from these main shocks and a number of aftershocks were recorded at the Icelandic strong motion network operated by the University of Iceland. At one of the instrumented sites considerable amplification was recorded on lava-rock overlying alluvial deposits. This site fits poorly in the soil classification systems of most earthquake codes. In this paper the recorded data is analyzed with different methods and the results are compared with the results of a one-dimensional site response analysis. The different methods produce the same characteristic of soil amplification at the site. The findings of this study have important implications for design criteria for sites with similar geology.

A pockmark field in the Patras Gulf (Greece) and its activation during the 14/7/93 seismic event

During a recent oceanographical-geophysical survey carried out in the southeastern part of the Gulf of Patras in Western Greece for the construction of an outfall, an active pockmark field was found. The pockmark field was formed in soft layered Holocene silts. The pockmarks are associated with acoustic anomalies attributed to gas-charged sediments. The pockmarks vary in size and shape from 25 to 250 m in diameter and from 0.5 to 15 m in depth and are among the largest and deepest observed in the world. On July 14th, 1993, during the survey, a major earthquake of magnitude 5.4 on the Richter scale occurred in the area. During the 24 hour period prior to the earthquake the bottom water temperature anomalously increased on three occasions, whilst for a few days after the earthquake it was noted that the majority of the pockmarks were venting gas bublles. It is considered that the three abrupt sea-water temperature increases were probably the result of upward migrating high-temperature gas bubbles in the water column. It is further suggested that the earthquake was the triggering mechanism and that the gas expulsion was caused by the reduction in the pore volume in the sediments resulting from changes in the stress regime prior to the earthquake. Therefore, it can be suggested that in seismic areas adjacent to pockmark fields, earthquake prediction may be achieved by monitoring the water temperature and/or the rate of gas venting in the pockmark field. Our analysis indicates that the pockmark field in the Patras Gulf has formed slowly during the Holocene by continuous gas venting, which is periodically being interrupted by short-duration events of enhanced gas seepage triggered by earthquakes.

Case histories of some artificial crustal disturbances

The Shivajisagar lake area of the Koyna Hydroelectric Project, situated in the Deccan Trap region of the aseismic Indian Shield began to exhibit mild seismicity immediately after the impounding of the reservoir in 1963. This mild seismicity culminated in a major earthquake of magnitude 7.0 on December 10, 1967, followed by numerous aftershocks of diminishing magnitude and frequency, obeying a relationship of the type t − b . It has been observed that a significant part of these earthquakes, especially the aftershocks, was found to be correlated with reservoir water load. In the case of a few new water reservoirs in India, situated mostly in marginal areas of the aseismic Indian Shield, very minor seismic activity, though of an isolated nature, was recently noticed after impounding. On the other hand, very large reservoirs situated well inside the stable Indian Shield, did not exhibit any noticeable seismic activity after impounding. Studies with an ultra-high-sensitivity seismograph (magnification∼ 10 6) near a newly impounded reservoir in the Deccan Trap reveal evidence of the occurrence of minute tremors of magnitude below zero. Thus, the geographical distribution of the above water reservoirs exhibiting seismic activity implies the probable influence of a geotectonic pattern in the process.