Diurnal variations of outgoing long wave radiation (OLR) vis a vis 4 January, 2016 Manipur earthquake (Mw: 6.7): An earthquake precursor?

Daily and diurnal variations of OLR from INSAT 3D and Kalpana satellites have been studied during 25 December, 2015 to 5 January, 2016 over the epicentral region of the Manipur earthquake of 4 January, 2016 (Mw 6.7) and other regions within the view of these satellites. The surface temperatures recorded at Imphal around 30 km from epicentre of this earthquake were also examined. It is found that OLR remained low prior to the occurrence of Manipur earthquake while much larger rise occurred over several other regions where no significant seismic activity was reported. The results corroborate inferences reported in earlier studies that OLR or temperature changes are related to meteorological causes and its sole identification as earthquake precursor may be misleading due to poor constraints.

Post-earthquake hazard assessments might become rapidly ineffective under rapidly-evolving landslide controls

<p>Strong earthquakes, especially on mountain slopes, generate unconsolidated deposits of regolith, prone to remobilization by aftershocks and rainstorms. Assessing the hazard they pose and what controls their remobilizations in the years following the mainshock has not yet been attempted, primarily because of the lack of multitemporal landslide inventories. By exploiting a multitemporal inventory (2005–2018) covering the epicentral region of the 2008 Wenchuan earthquake and a set of predictor variables (seismic, topographic, and hydrological), we perform statistical tests to understand the evolution of controlling factors for debris remobilization in time. Our analyses, supported by a random-forest susceptibility assessment model, reveal a prediction capability of seismic-related variables depleting with time, as opposed to hydro-topographic parameters gaining importance and becoming predominant within a decade. Results may have important implications on the way conventional susceptibility/hazard assessment models should be employed in areas where coseismic landslides are the main sediment production mechanism on slopes.</p>

How Has GPS Velocity Field Changed Along the 1999 Izmit Rupture 20 Years After the 1999 Izmit, Turkey Earthquake?

<p>A seismic gap along the western segment of the North Anatolian Fault, in the Marmara-Izmit region, was identified before the 1999 M7.6, Izmit and M7.4 Duzce earthquakes, so the region along the coseismic fault has been monitored with geodetic techniques for decades, providing well defined pre-, co- and post-seismic deformations. Here, we report new continuous and survey GPS measurements with near-fault (~2 – 10 km to the fault) and far-fault (~50 – 70 km from the fault) stations, including 7 years (2013 – 2019) of continuous observations, and 5 near-fault campaigns (every six months between 2014 – 2016) to further investigate postseismic deformation. GPS observations were processed with the GAMIT/GLOBK (v10.7) GNSS software. We used these observations to estimate the spatial distribution of current aseismic after-slip, along the 1999 Izmit rupture. We also searched for spatiotemporal changes of shallow creep events along the surface trace. With elastic models and GPS observations, we determined a shallow creep rate that reaches a maximum around the epicenter of the 1999 Izmit earthquake of about 12.7 ± 1.2 mm/yr, consistent with published InSAR results. Creep rates decrease both east and west of the epicentral region. Moreover, we show that broad-scale postseismic effects that diminish logarithmically, continue at present. (This study is supported by TUBITAK 1001 project no: 113Y102 and 117Y278)</p>

The July 2019 Ridgecrest, California, Earthquake Sequence Recorded by Creepmeters: Negligible Epicentral Afterslip and Prolonged Triggered Slip at Teleseismic Distances

We report sequential triggered slip at 271–384 km distances on the San Andreas, Superstition Hills, and Imperial faults with an apparent travel-time speed of 2.2 ± 0.1 km/s, following the passage of surface waves from the 4 July 2019 (17:33:49 UTC) Mw 6.4 and 6 July 2019 (03:19:53 UTC) Mw 7.1 Ridgecrest earthquakes. Slip on remote faults was not triggered instantaneously but developed over several minutes, increasing in duration with distance. Maximum slip amplitudes varied from 10 μm to 5 mm within minutes of slip nucleation, but on the southernmost San Andreas fault slip continued for two months and was followed on 16 September 2019 by a swarm of microearthquakes (Mw≤3.8) near Bombay Beach. These observations add to a growing body of evidence that fault creep may result in delayed triggered seismicity. Displacements across surface faults in the southern epicentral region and on the Garlock fault in the months following the Ridgecrest earthquakes were negligible (<1.1 mm), and they are interpreted to characterize surface strain adjustments in the epicentral region, rather than to result from discrete slip on surface faults.

Damage assessment and seismic behavior of steel buildings during the Mexico earthquake of 19 September 2017

During the 19 September 2017 earthquake, steel buildings in the States of Morelos, Puebla, Mexico, and Mexico City were subjected to severe ground shaking. Despite in some cases, moderate damages in non-structural elements were developed; generally, null or minor structural damage was reported. The notable exceptions are (1) a three-stories building located at the southern area of Mexico City and (2) some schools near to the epicentral region in the State of Morelos. The behavior of these buildings is analyzed in detail. Conclusions are drawn on the demands imposed on steel structures considering the actual demands in order to underline the relevance of the normative design procedures.

Geological and geophysical system “tectonics-seismicity” of the unique Khailinsk center of high-magnet swarm. South-west of the Koryak seismic belt

Хаилинский центр уникальное явление в Корякском сейсмическом поясе, который обрамляет на севере литосферную плиту Берингию. Он создан роем Хаилинского и Олюторского землетрясений и афтершоков с М 5,07,6. Центр лежит в погруженной глыбе литосферы Олюторского залива, созданной межглыбовыми СЗ разломами на бортах трога с глубиной 82 км в рельефе литосферы. На трог надвинуты морские террейны с максимальным прогибом горизонтов литосферы в их килях, через которые проходит колонна с гипоцентрами землетрясений. Высокомагнитудный рой землетрясений Хаилинского Центра имеет взаимно ортогональные эллипсы афтершоков при общих эпицентрах главных толчков. Хаилинское землетрясение не проявило традиции связи эллипса релаксации афтершоков с известной геологией афтершоков в плане и разрезе. События столь мощные, не увязанные с очевидной геологической структурой представляются очевидной новинкой в мировой горнодобывающей практике. Анализ Хаилинского и Олюторского событий выявил коллизию двух фактов: совпадение эпицентров и полную ортогональность облаков обоих землетрясений. Их исследование как элементов одной системы тектоника-сейсмичность определило геологическое пространство положения гипоцентров. Интерес к сейсмичности Хаилинского высокомагнитудного центра рассматривается как обращение в геологии окраины к уникальной малой литосферной плите Берингия в сейсмологии СВ Азии. В основу исследования системы тектоника-сейсмичность положена концепция сейсмогенной тектоники территории активной окраины континента СВ Азии и места в ней Хаилинского Центра высокомагнитудного роя (ХВЦ). Основы такого понимания сейсмичности окраины территории тектоники определены авторской Концепцией глыбово-клавишной структуры литосферы на активной окраине континента . Эпицентральная область Хаилинского и Олюторского землетрясений локализуется на площади локальной Тылговаямской впадины, причленённой к Вывенской впадине с юга на её висячем ЮВ крыле зоны Вывенского разлома The Khailinsk Center is a unique phenomenon in the Koryak seismic belt, which frames the Beringia lithospheric plate in the north. It was created by a swarm of Khailinsk and Olyutorsk earthquakes and aftershocks with M 5.07.6. The center lies in a submerged block of the lithosphere of the Olyutor Bay, created by interblock northwestern faults on the sides of the trough with a depth of 82 km in the relief of the lithosphere. Sea terranes with a maximum deflection of the lithosphere horizons in their keels, through which a column with earthquake hypocenters passes, are thrust onto the trough. The high-magnitude swarm of earthquakes of the Khailinsk Center has mutually orthogonal ellipses of aftershocks at common epicenters of the main shocks. The Khaili earthquake did not show the tradition of connecting the aftershock relaxation ellipse with the known aftershock geology in plan and section. Such powerful events that are not tied to an obvious geological structure seem an obvious novelty in world mining practice. An analysis of the Khailinsk and Olyutor events revealed a collision of two facts: the coincidence of the epicenters and the complete orthogonality of the clouds of both earthquakes. Their study as elements of one system tectonics-seismicity determined the geological space of the hypocenters position. The interest in the seismicity of the Khailinsk high-magnitude center is considered as an appeal in the geology of the outskirts to the unique small lithospheric plate Beringia in the seismology of NE Asia. The research basis of the tectonics-seismicity system is the concept of seismogenic tectonics in the territory of the active margin of the North Asian continent and the place of the Khailinsk Center for High Magnitude Swarm (KHC). The basics of such understanding of the seismicity in the outskirts of the territory tectonics are determined by the authors Concept of the block-key structure of the lithosphere on the active outskirts of the continent. The epicentral region of the Khailinsk and Olyutorsk earthquakes is localized on the area of the local Tylgovyamsk Depression, connected to the Vyvensk Depression from the south on its hanging SE wing of the Vyvensk Fault zone

METHODOLOGICAL APPROACHES TO DETERMINING THE STATE OF BLOCK SEISMOGENIC MEDIUM ON THE EXAMPLE OF THE 2008-2011 SEISMIC ACTIVATION IN THE CENTRAL PART OF THE BAIKAL RIFT

Based on the joint analysis of the seismic regime parameters, such as anomalies of seismic energy release, b-value, seismic activity A10, approaches to assess the state of the block-seismic medium are proposed. The method validation was done for the example of preparation and development of seismic activity in 2008-2011 in the Central part of the Baikal rift, during which there were 2 strong M5.3 earthquakes. It was found that within 2 years before the strong Maximihinskoye Earthquake of 2008 in the Earth's crust of the epicentral region there is a transformation from softening to strengthening (consolidation) of the block medium. At the same time, in the neighboring region (the area of the Svyatoy Nos Peninsula), the opposite nature of the changes is observed.