SEISMICITY of the CARPATHIANS in 2015

The article describes seismic observations in the Carpathian region in 2015, which were carried out, as before, by two organizations from two states: in Ukraine – the Seismicity department of the Carpathian region of the Institute of Geophysics of the NAS of Ukraine, in Moldova – the Seismology laboratory of the Institute of Geology and Seismology of the Academy of Sciences of Moldova. 20 stationary digital stations with a processing center in L'viv and six stations with a center in Chisinau operated in Ukraine and Moldova respectively. Different programs, local hodographs and magnitudes were used. The consolidated catalogue of earthquakes was created in L'viv. The total number of earthquakes in 2015 was NΣ=164 in the ranges: KR=4.7–12.2, h=1–160 km. The total seismic energy ΣE=5.381012 J. 23 earthquakes with depths h=50–160 km were located in the Vrancea zone. The maximum earthquake with KR=12.2 was registered on January 24 in the Vrancha mountains with hрР=89 km. In the Precarpathian region, nine events with energy classes KR=4.7–8.9 were registered, the total seismic energy of which is ΣЕ=1.25109 J. Increased seismic activity was observed in Transcarpathia. A series of tangible earthquakes with aftershocks was recorded in the Tyachiv area. Their total number was NΣ=77. The strongest tangible earthquake occurred in the area of Okrugla village on July 19 with KR=11.1. The earthquake source is located in the Earth's crust at a depth of h=7.7 km. The earthquake was felt by the population in the epicentral area with an intensity of I=6. In addition, this earthquake, like 5 others, was felt in the territory of northern Romania. In general, a decrease in the seismicity level in the Carpathians in 2015 was observed compared to that in 2013 and 2014.

ANALYSIS OF A PEAK GROUND ACCELERATION VALUE AND EARTHQUAKE INTENSITY USING DONOVAN METHOD IN BANTEN PROVINCE

Analysis of a peak ground acceleration value and earthquake intensity in Banten Province has been carried out using historical earthquake data from 2008 to 2018. This research aims to describe a prone area of the earthquake. The specification of data was a magnitude > 5 SR and the depth 0-70 km. The Donovan method was used to analyze peak ground acceleration value and the earthquake’s intensity. According to the data obtained, 31 earthquake points with a maximum earthquake strength occurred on October 16, 2019, with a depth of 10 km and a magnitude of 6.48 SR. This earthquake was located in Ujung Kulon with coordinates -6.81 LS and 105.113 BT. Based on data analysis result was obtained a peak ground acceleration value and the intensity of earthquake maximum in The Pandeglang Regency with a peak ground acceleration value was 211.56 cm/s2, and intensity of scale VIII and a large risk level of three. While a peak ground acceleration minimum is located in the South Tangerang City was 62.82 cm/s2 with a scale of intensity VII and a moderate risk level.

CARPATHIANS

The article describes seismic observations in the Carpathian region in 2014, which were carried out, as before, by two organizations from two states: in Ukraine – the Seismicity Department of the Carpathian region of the Institute of Geophysics of the National Academy of Sciences of Ukraine, in Moldova – the Seismology Laboratory of the Institute of Geology and Seismology of the Academy of Sciences of Moldova. In Ukraine, 20 stationary digital stations and 3 temporary ones worked in the Dniester energy complex with a processing center in Lviv, in Moldova - six stations with a center in Chisinau. Different programs, local hodo-graphs and magnitudes were used. The consolidated catalog of earthquakes was created in Lviv. A map of epi-centers and a table of the distribution of earthquakes of different classes by region are given. The total number of earthquakes in 2014 was NΣ=81 in the range KP =5.2–14.3 with the interval of hypocenter depths h=1–154 km and the total seismic energy ΣE=2.11·1014 J. Of these, 18 earthquakes with depths h=77–154 km located in the Vrancea zone. The maximum earthquake with KP=14.3 was registered on November 22 in the Precarpathian Trough with hрР=37 km. In the Vrancha mountains the maximum earthquake occurred on March 29 with the KP=12.5 and hрР=136 km. In the Precarpathian and Transcarpathian regions, all earthquakes were weaker. The most powerful event in Transcarpathia was a perceptible earthquake that occurred near the Trostnyk seismic station on November 15 with KP=8.9. The earthquake source is located in the Earth's crust at a depth of h=10 km. The earthquake was felt by the population of the Dyakovo, Trostnyk, Fanchykovo villages with the intensity of 5 and 4–5. In general, in all the seismically active zones of the Carpathians in 2014, there was a slight increase in the level of seismicity compared to that in 2013.

GLOBAL EARTHQUAKES

The information on global seismicity in 2014 at the level of strong earthquakes with M≥6 according to the Seismological Bulletin of the Geophysical Survey of RAS (GS RAS) is provided. The original Seismological Bulletin for 2014 contains parameters of 3268 earthquakes in the world, versus 4212 in 2013. This article analyzes 165 earthquakes with M≥6, including 16 strongest earthquakes with M≥7, and five earthquakes with M6.0–6.7, which resulted in significant casualties and destruction. The information on focal mechanisms, macroseismic effect, the number of victims, tsunamis, etc. is given. A comparative analysis of the number of earthquakes and released seismic energy in different seismically active regions of the Earth showed that, as before, the Pacific region was the most seismically active. More than 96 % of common seismic energy was re-leased in the Pacific region, compared to 1.8 % in Eurasia, 1.3 % in Atlantic Ocean and 0.2 % in the Indian Ocean. The Earth’s maximum earthquake in 2014 occurred on April 1 with Mw=8.1 off shore of Chile. It was accompanied by numerous foreshocks and aftershocks. The maximum casualties and material damage in 2014 were caused by the catastrophic Ludian earthquake that occurred on August 3 with MS=6.2 in the Chinese province of Yunnan.

A Study on the Largest Hydraulic-Fracturing-Induced Earthquake in Canada: Observations and Static Stress-Drop Estimation

ABSTRACT On 17 August 2015, an Mw 4.6 earthquake occurred northwest of Fort St. John, British Columbia, possibly induced by hydraulic fracturing (HF). We use data from eight broadband seismometers located ∼50 km from the hypocenter to detect and estimate source parameters of more than 300 events proximal to the mainshock. Stress-drop values estimated using seismic moment and corner frequency from single-event spectra and spectral ratios range from ∼1 to 35 MPa, within the typical range of tectonic earthquakes. We observe an ∼5-day delay between the onset of fluid injection and the mainshock, a b-value of 0.78 for the sequence, and a maximum earthquake magnitude larger than the prediction based on the total injection volume, suggesting that the Mw 4.6 sequence occurred on a pre-existing fault and that the maximum magnitude is likely controlled by tectonic conditions. Results presented here show that pre-existing fault structures should be taken into consideration to better estimate seismic hazard associated with HF operations and to develop schemes for risk mitigation in close proximity to HF wells.

Geometric controls on megathrust earthquakes

SUMMARY The role of subduction zone geometry in the nucleation and propagation of great-sized earthquake ruptures is an important topic for earthquake hazard, since knowing how big an earthquake can be on a given fault is fundamentally important. Past studies have shown subducting bathymetric features (e.g. ridges, fracture zones, seamount chains) may arrest a propagating rupture. Other studies have correlated the occurrence of great-sized earthquakes with flat megathrusts and homogenous stresses over large distances. It remains unclear, however, how subduction zone geometry and the potential for great-sized earthquakes (M 8+) are quantifiably linked—or indeed whether they can be. Here, we examine the potential role of subduction zone geometry in limiting earthquake rupture by mapping the planarity of seismogenic zones in the Slab2 subduction zone geometry database. We build from the observation that historical great-sized earthquakes have preferentially occurred where the surrounding megathrust is broadly planar, and we use this relationship to search for geometrically similar features elsewhere in subduction zones worldwide. Assuming geometry exerts a primary control on earthquake propagation and termination, we estimate the potential size distribution of large (M 7+) earthquakes and the maximum earthquake magnitude along global subduction faults based on geometrical features alone. Our results suggest that most subduction zones are capable of hosting great-sized earthquakes over much of their area. Many bathymetric features previously identified as barriers are indistinguishable from the surrounding megathrust from the perspective of slab curvature, meaning that they either do not play an important role in arresting earthquake rupture or that their influence on slab geometry at depth is not resolvable at the spatial scale of our subduction zone geometry models.

Maximum Earthquake Size and Seismicity Rate from an ETAS Model with Slip Budget

ABSTRACT We define a seismicity model based on (1) the epidemic-type aftershock sequence model that accounts for earthquake clustering, and (2) a closed slip budget at long timescale. This is achieved by not permitting an earthquake to have a seismic moment greater than the current seismic moment deficit. This causes the Gutenberg–Richter law to be modulated by a smooth upper cutoff, the location of which can be predicted from the model parameters. We investigate the various regimes of this model that more particularly include a regime in which the activity does not die off even with a vanishingly small spontaneous (i.e., background) earthquake rate and one that bears strong statistical similarities with repeating earthquake time series. Finally, this model relates the earthquake rate and the geodetic moment rate and, therefore, allows to make sense of this relationship in terms of fundamental empirical law (the Gutenberg–Richter law, the productivity law, and the Omori law) and physical parameters (seismic coupling, tectonic loading rate).

GLOBAL EARTHQUAKES

The information on the Earth seismicity in 2013 at the level of strong earthquakes with M≥6 is provided according to the Seismological Bulletin of the Geophysical Survey of RAS (GS RAS). The initial Seismo-logical Bulletin for 2013 contains parameters of 4212 earthquakes in the world, versus 4845 in 2012. This article analyzes parameters of 160 strong earthquakes of the Earth in 2013 with M≥6, including 24 strongest earthquakes with M≥7 and the maximum earthquake of the Earth with Mw8.3 occurred in Okhotsk Sea, as well as four earthquakes with M6.0–6.8, which resulted in significant sacrifices and destructions. The location of earthquake epicenters and seismic stations, whose data were used to deter-mine the main parameters of earthquake foci, are shown, as well as a comparative analysis of the number of earthquakes and seismic energy released within the Earth's seismic regions is given. The information on focal mechanisms and consequences of 28 strongest earthquakes, including macroseismic effect, number of victims, landslides, tsunamis, etc. is given. The epicenters of most of them are confined to the boundaries of the largest tectonic plates of the Earth, and their focal mechanisms correspond to the basic laws of plate movement. The hypocenters of most of the strongest earthquakes are located within the Earth's crust, with the exception of earthquakes in Colombia, the Kuril Islands and south of the Fiji Is-lands, which had intermediate depths (h=98–171 km), and the strongest in 2013 Okhotsk earthquake, the source of which lay in the upper mantle at the depth of h=617 km. The movement in the source of the Okhotsk earthquake corresponds to the subduction process of the Pacific plate under the continent and indicates that the subducted plate is at the depth of 617 km.

Analisis Kestabilan Lereng di Bukit Tui Section S0° 28’ 50.23” E100° 24’ 16.89”- S0° 28’ 49.19” E100° 24’ 17.07” Kecamatan Padang Panjang Barat Kota Padang Panjang

Tui Hill is a limestone hill lined south of Padang Panjang, located between Rao-Rao Village to Tanah Hitam. The results of research at Tui Hill at the location S0° 28’ 50.23” E100° 24’ 16.89”- S0° 28’ 49.19” E100° 24’ 17.07” located in Tanah Hitam Village has a covered dolomite rock slope. Based on the Indonesian earthquake zoning map, the city of Padang Panjang is classified as a high earthquake vibration zone, ranging from 0.8-0.9 g. The potential for landslides on the slopes of the study can lead to the closure of the access road to dolomite mining so that it can hamper road user traffic and disrupt mining production as well as potential material losses and fatalities This study aims to determine the Safety Factors on earthquake slope research and recommendations to increase the value of Safety Factors (FK). Based on the results of the analysis by simulating earthquake vibration values the maximum earthquake vibration values that can be held by slopes in a safe condition is 0.2 g or equivalent to 6.4-6.6 on the Richter Scale, namely with FK of 1,281. Then, the author issued for the slope by changing the slope of the slope from 53˚ to 25˚ increases can obtain a slope FK value of 1.438, according to Joseph E. Bowles (1984) the slope is in accordance with the safe conditions.