Kuril Islands experienced a magnitude 8.3 earthquake on November 15, 2006 at 11:14:13 UTC and another earthquake a few months later of magnitude 8.1 on January 13, 2007 at 04:23:21 UTC according to Wikipedia. Which is considered a doublet. A doublet are earthquakes who have similar waveforms. The purpose of this notebook is to analyze the waveforms of both earthquakes.

The Kivu Rift which is very seismically active, is a part of the western branch of the East African Rift System and has recorded major earthquakes. Intense seismicity was observed and felt between 1997 and 2000 and was reported by CRSN/Lwiro. That resurgence of seismicity resulted in the occurrence of the earthquakes of 2002, 2008 and 2015 which caused a lot of damage in the region. Based on the ISC seismicity catalog, the analyze of seismicity of this rift between 2000 and 2015 as well as the frequency composition by spectrogram, the autopicking of the important seismic phases were the goal of this project. The download data was based on a radius of 2.5° around the Lwiro station, since three major earthquakes occurred in areas close to it and particularly in the seismic zone of Lake Kivu. The temporal, frequency and spatial analysis was done under python jupyter notebook. The minimum and maximum magnitude reported in this catalog are respectively 1.1 and 6.2 with the average of 3.2. In general, earthquakes occurred at shallow depths for an average of 8.4 km and a maximum of 39.9 km. Some earthquakes were very shallow between 0 and less than 10 km. Most earthquakes were occurred at 10 km and some for magnitudes between 2 and 4 mostly. The low magnitudes correspond particularly to the intense activity during aftershocks sequences of major shocks and also to the contribution of the local network (KivuSnet); and this is also the observation related to deeper and weaker earthquakes and particularly between 2008 and 2015. This local network has also contributed to increasing the number of earthquakes reported in the catalog. The major earthquakes of 2002, 2008 and 2015 have superficial and moment magnitudes of 6.2, 5.9 and 5.8 respectively. The spatial distribution shows a concentration of events in Lake Kivu in the Virunga volcanic region. The 3D analysis shows that the strong earthquakes occurred at shallow depths while for certain weak magnitudes (less than 4) are at great depths. The analyze of the waveform from the 2015 earthquake at the nearest MBAR station shows the presence of the two different shocks for which the spectrogram has made it possible to identify the beginnings of the waves and their P and S phases respectively. The bandpass filter (3 - 6 Hz) associated with the analysis of detection by triggering and autopicks made it possible to discriminate its beginnings in the spectrogram, and facilitated to identify the P and S phases which were compared to those provided by IRIS ( Wilber3). the first earthquake starting at 50 seconds has for P: 2015-08-07T01:25:40.019 and S: 2015-08-07T01:26:10.019 and for the second which starts at 214 seconds has for P: 2015-08-07T01 :29:14 and S:2015-08-07T01:29:45. depending on the distance (2.4°) between the MBAR station and the high frequency (Hz) event, it is clear that the earthquake is of the tectonic type.

This project will be dedicated to study the seismicity of a limited area from San Juan, Argentina. San Juan is located in the andean backarc, where we have a subduction zone with the Nazca plate subducting below the South American plate. The project will be focused on a circular area centered in Sierra Pie de Palo, this area was chosen because historically large events have happened. One example is the Mw 7.4 earthquake that occurred in 1977 that produced catastrophic consequences.

On October 17, 2021, a seismic swarm began in the Department of Jutiapa, Guatemala, of which 1,099 earthquakes were recorded. Due to their location and depth, they were reported by residents of the municipalities of Conguaco and Moyuta, generating alarm due to the tremor perceived and the frequency with which they occurred. The area of activity of this swarm is located in an area of complex geology. To the north of Conguaco is the Jalpatagua fault with clockwise movement and to the southeast the Aguachapan fault, thus forming a pull-apart basin. To the southwest is the Moyuta volcano, which is considered active and in which areas of significant geothermal activity have been identified. For this reason, this area is of research interest because the origin of these earthquakes has not yet been determined, in addition to being an active area that is changing, so it is important to have more data and determine the risk in this region.

A Study of Two Large Earthquakes in Southern Asia (Nepal - Himalayan Region) [V G Rao Kambala, Department of Theoretical Geophysics, IGF-PAN, Warsaw, Poland] An earthquake is an intense shaking of the Earth’s surface. The vibration is caused by movements in Earth’s outermost layer. An earthquake is the result of a sudden release of stored energy in the Earth's crust that creates seismic waves. The magnitude of an earthquake is conventionally reported using the Richter scale or a related Moment scale (with magnitude 3 or lower earthquakes being hard to notice and magnitude 7 causing severe damage over large areas). Now we will discuss about two large earthquakes based on their seismogram collected from stations. First, we will know some basic information about these two earthquakes, then will collect data, and plot them both as a seismogram & also a spectrogram. So what is a spectrogram? A spectrogram is a visual way of representing the signal strength, or “loudness”, of a signal over time at various frequencies present in a particular waveform. Not only can one see whether there is more or less energy at, for example, 2 Hz vs 10 Hz, but one can also see how energy levels vary over time. Why we will use a spectrogram to study earthquakes? When an earthquake occurs the spectrogram will show ground motions that typically last from several tens of seconds to many minutes depending on the size of the earthquake and the sensitivity of the seismograph. Almost any earthquake in the world having a magnitude greater than 5.5 will be seen on these spectrograms. So, it is a visual way to represent earthquake intensity. 1: 2016 Imphal earthquake The strong M 6.7 earthquake was recorded before dawn Monday near the India-Myanmar border at 4:35 a.m. (6:05 p.m. ET Sunday) 20 miles west-northwest of Imphal, India, the capital of Manipur state. Moderate to strong ground shaking was also reported in the far eastern part of India as well as parts of neighboring Bangladesh where thousands of people rushed into the streets of Dhaka, which lies about 350 km (220 miles) from the epicenter of the quake. 2: April 2015 Nepal earthquake (also known as the Gorkha earthquake) magnitude 7.8 earthquake struck Nepal on April 25, 2015, toppling multi-story buildings in Kathmandu, the capital, and creating landslides and avalanches in the Himalaya Mountains. Nearly 9,000 people died and more than 22,000 suffered injuries. It was the deadliest earthquake in the seismically active region in 81 years. The earthquake triggered an avalanche on Mount Everest, killing 21, making 25 April 2015 the deadliest day on the mountain in history. The earthquake triggered another huge avalanche in the Langtang valley, where 250 people were reported missing. Hundreds of thousands of Nepalese were made homeless with entire villages flattened, across many districts of the country. Continued aftershocks occurred throughout Nepal at intervals of 15–20 minutes, with one shock reaching a magnitude of 6.7 on 26 April at 12:54:08 NST.

The Mw 7.0 Samos earthquake was the deadliest earthquake in 2020 causing 119 fatalities (Mavroulis et al., 2022). It occurred at 11:51 UTC (1:51 pm local time) in the Aegean Sea and was felt across Turkey and Greece. The rupture resulted in a significant energy release and generated a localized tsunami. Initially many key earthquake source characteristics were unclear, with significant discrepancies in strike/dip/rake as well as centroid location and time (Cetin at al., 2020). Now most of the earthquake kinematics have been resolved (Lentas et al., 2021; Chousianitis and Konca, 2021; Taymaz et al., 2022) and it seems resolved that the earthquake rupture on a north-dipping E-W striking normal fault known under several names (Plicka et al., 2021), such as Samos Basin Fault (Nomikou et al., 2021), Kaystrios Fault (Caputo and Pavlides, 2013) or as North Samos Fault (Chatzipetros et al., 2013). While the island of Samos experienced mainly vertical uplift (cf. GPS data from station SAM3), the Gulf of Kuşadası (Turkish: Kuşadası Körfezi) coseismically subsided sourcing the subsequent tsunami, which was influenced by large fault slip to the west of the hypocentre in combination with trapped energy in the semi-closed bay and local resonance effects of the tsunami leading to amplification of wave height (Hu et al., 2022). The tsunami had a strong local focus with 2.31 m maximum inundation height and 3.82 maximum runup height (Cetin et al., 2020). No tide gauges are available in the near-field within the Kushada gulf, but further located stations in the Aegean Sea recorded the tsunami and are analysed in this Notebook. I first provide a brief overview of the earthquake and the region of interest, investigate GPS and tide gauge motions and request seismic data with the goal to better understand the impact of the 2020 Samos earthquake and tsunami.

The southwestern Taiwan earthquakes of 2006 December 26, 12:26 UTC (M = 7.1) and 12:34 UTC (M = 6.9) occurred in a zone of transition along the north-south boundary between the Eurasian plate and the Philippine Sea plate. The Eurasian plate is moving east-southeast with respect to the Philippine Sea plate at a velocity of about 80 mm/y. Along the plate-boundary south of Taiwan, the Eurasian plate is oceanic lithosphere, and convergence is mostly accommodated by the subduction of the Eurasian plate beneath the Philippine Sea Plate. The subducted Eurasian plate is seismically active to depths of about 200 km offshore of southeastern Taiwan, to the east-southeast of the December 26 shocks. North along the plate boundary from southwestern Taiwan to northern Taiwan, by contrast, the Eurasian plate is buoyant continental lithosphere that resists subduction, and a significant fraction of plate convergence is accommodated by intense compressional deformation of the earth's crust rather than by subduction of one plate beneath the other. Preliminary focal-mechanism solutions indicate that the earthquake of 12:26 UTC occurred as the result of normal faulting and that the earthquake of 12:34 UTC occurred as the result of predominantly strike-slip faulting. The normal-faulting focal-mechanism of the shock of 12:26 UTC suggests that this shock occurred as the result of intraplate stresses within the subducting Eurasian plate. Normal-faulting focal-mechanisms are commonly observed in the shallow parts of subducting plates; the causative stresses are generated by the bending of the subducting plates. A normal-fault focal-mechanism is not consistent with the earthquake having occurred as the result of shallow compressional deformation between two converging plates which each consist of buoyant lithosphere. Presently available evidence does not permit a confident statement on the whether the earthquake of 12:34 UTC occurred as the result of shallow deformation caused by convergence between two plates consisting of buoyant lithosphere or instead occurred as the result of deeper deformation within a subducted and deformed Eurasian plate. The style of faulting preliminarily inferred for the shock of 12:34 UTC, right-lateral strike-slip faulting on a northeast striking fault or left-lateral faulting on a north-northwest striking fault, would be consistent with the style of faulting that has been observed at the surface in southwestern Taiwan and that helps accommodate the mutual convergence of buoyant Eurasian lithosphere and Philippine Sea lithosphere. It is possible, however, that this style of faulting could also occur as the result of intraplate stresses within the subducting Eurasian plate, beneath its boundary with the Philippine Sea plate.

The short study is focused on understanding the earthquake activity and its spectrograms associated with the 2020 Caribbean earthquake of M 7.7, which is the largest to occur in the Caribbean region since 1946. The earthquake caused a minor tsunami and caused panic for people living around it's epicentral region. Though, the event is not destructive owing to its distance from major settlements and other man made features, it caused aftershock activity, with largest of them being the MW 6.1. For this study, the seismograms were requested using the IRIS webservices client for Obspy. The data has been downloded for the 24 period surrounding the mainshock. The results reveal that (i) the 2020 Caribbean earthquake of M 7.7 is associated with aftershocks of various size with the largest being M 6.1, (ii) the mainshock occurred almost instantaneously without any foreshock activity. The spectrograms reveal that the mainshock (M 7.7) and its largest aftershock (M 6.1) release energy in very low frequency range (<1 Hz), while the smaller aftershocks (M<5.0) dominate the higher frequencies upto 10 Hz. Further, the study suggests that the modern scientific computational tools such as jupyter notebooks and python and IRIS web services are very efficient and useful for seismological research.

In 2015, Nepal experienced a major 7.8 Mw earthquake that killed several thousand people. This, the Gorkha Earthquake was one of the most important recent seismological events in the Himalayas. For many decades there were few to no good, well-recorded events in this part of the world, especially few were the 'great' earthquakes (Mw > 8.0) which are so essential to understanding the changes this mountain range undergo morphologically. In this notebook, I seek to analyze this event and report on what is found.

The Albertine Rift is the western branch of the East African Rift, covering parts of Uganda, the Democratic Republic of Congo (DRC), Rwanda, Burundi and Tanzania. It extends from the northern end of Lake Albert to the southern end of Lake Tanganyika. This area includes the most important geological and geophysical features of the West African Rift Valley, such as the Kivu and Ruzizi basins, the Virunga volcanoes, the Lake Edouard trough, the Ruwenzori Horst and the Lake Albert trough. It is characterized by the most significant uplift and complex crustal dislocation, accompanied by the most intense volcanism in the West African Rift Valley. A brief analysis of the Albertine Rift seismicity in the western part of the East African Rift over the last 32 years was performed. It was found that most of the seismic activity in this region is shallow (less than 40 km) and that the epicenters of the events (generally less than magnitude 5.5) are perfectly aligned with the rift. Although the energy is distributed over the entire region, we found that the activity is much more concentrated between lakes Eduard and Tanganyika and it is in this same part of our area that we found more low-energy events (with magnitude less than 3). Given the presence of active volcanoes (Nyiragongo and Nyamulagira) and the danger they represent for the local population, the reinforcement of seismic monitoring techniques in this part of the West African Rift remains very useful and of concern.

In this study it is attempted observe the variation of seismogram characteristic of at three azimuths around the Andaman islands. The above analysis shows that in the near station like in Thailand and Srilanka the event is recorded and spectrograms signifies frequency lies between 1 to 7.5 hertz. The characteristic that the PALK station and COCO station has very uniform energy at all time period(200s to 1800s) in contrast to CHTO which have dominant frequecy in the time of 400s to 800s. So, we can say that in case of CHTO the energy is decaying exponentially , in comparison to the other two stations , which show some shorts of more anisotropic behaviour along the direction of CHTO.