Abstract Relocation of earthquakes recorded by the agency for meteorology, climatology and geophysics (BMKG) in Indonesia inversions global positioning system (GPS) data reveal clear seismic gaps to south island Java. These may be related potential sources future megathrust region. To assess expected inundation hazard, tsunami modeling was conducted based on several scenarios involving large tsunamigenic generated ruptures along segments The worst-case scenario, which two spanning Java...

We estimated the energy radiated by earthquakes in southern California using on-scale very broadband recordings from TERRAscope. The method we used involves time integration of squared ground-motion velocity and empirical determination distance attenuation function station corrections. integral is typically taken over a duration 2 min after P-wave arrival. curve for obtained given q(r) = cr^(−n)exp(−kr)(r^2 Δ^2 + h_(ref)^2) with c 0.49710, n 1.0322, k 0.0035 km^(−1), h_(ref) 8 km, where Δ...

Statistics of earthquakes in California show linear frequency‐magnitude relationships the range M 2.0 to 5.5 for various data sets. Assuming Gutenberg‐Richter distributions, there is a systematic decrease b value with increasing depth earthquakes. We find consistent results sets from northern and southern that both include exclude larger aftershock sequences. suggest at shallow (∼0 6 km) conditions more heterogeneous material properties lower lithospheric stress prevail. Rupture initiations...

In the early morning (01:47 local time) of September 21, 1999, largest earthquake century in Taiwan (Mw=7.6, ML=7.3) struck central island near small town Chi‐Chi. The hypocenter was located by Central Weather Bureau Seismological Center at 23.87°N, 120.75°E, with a depth about 7 km. There were extensive surface ruptures for 85 km along Chelungpu fault vertical thrust and left lateral strike‐slip offsets. maximum displacement 9.8 meters is among movements ever measured modern earthquakes....

We compare the attenuation of high‐frequency (3–30 Hz) shear waves for crustal paths in New York State, South Africa, and southern California over source‐receiver distances about 10–400 km. The data consist digital recordings S (Δ = 5–100 km) Lg 100–400 produced by earthquakes. use a coda normalization method to remove effects site amplification source excitation from amplitudes waves. Over entire distance range studied (10–400 km), amplitude decay 3‐Hz wave energy is considerably less...

We have made observations of a heat signature that is associated with the frictional generated at time faulting for large earthquake. Temperature measurements in borehole intersects Chelungpu fault depth about 1100 m, show small increase near even six years after The temperature has symmetric shape width 40 m and centered on slipped 5 during 1999 Chi‐Chi, Taiwan amplitude 0.06°C observed anomaly indicates very low level friction

Dense record sections from deep earthquakes in Fiji and Argentina recorded on hundreds of short‐period stations California at distances 81° to 85° are used investigate the detailed P wave velocity structure above core‐mantle boundary (CMB). In data a secondary phase arriving 2 4 s after direct is identified as precursor PcP . This provides good evidence for reflection off top thin low‐velocity layer CMB. Comparisons synthetic seismograms indicate thickness 10 km reduction 5%–10% compared...

We investigated the mechanism of atmospheric oscillations with periods about 300 s which were observed for 1991 Pinatubo and 1982 El Chichón eruptions. Two distinct spectral peaks, at T = 270 230 eruption 195 266 eruptions, have been reported. found similar 1980 Mount St. Helens 1883 Krakatoa To explain these observations, we excitation problems two types idealized sources, “mass injection” “energy placed in an isothermal atmosphere. In general, modes oscillations, “acoustic” “gravity”...

We analyze the early aftershock activity of 2004 mid‐Niigata earthquake, using both earthquake catalog data and continuous waveform recordings. The frequency‐magnitude distribution analysis Japan Meteorological Agency (JMA) shows that magnitude completeness aftershocks changes from values around 5.0, immediately after main shock, to about 1.8, 12 hours later. Such a large incompleteness events can bias significantly estimation rates. To better determine temporal pattern in first minutes...

Large deep‐seated landslides occurred in Nara, Wakayama, and Mie prefectures of western Japan when Typhoon Talas passed through the region on September 3–4, 2011. Signals large have been recorded by seismic networks around world, overall force estimates previously determined for using long‐period waves. This study focuses high‐frequency waveforms presents signals 18 caused (2011). The location can be a seismological back‐projection technique these locations correlate with observed surface...

We investigate the early aftershock activity associated with four moderate earthquakes ( M w 6.6–6.7) that occurred recently in Japan. For each sequence, we examine continuous high-pass filtered seismograms recorded at seismic stations nearby main fault to identify as many events possible. The magnitude of these is calibrated using aftershocks are listed earthquake catalog Japan Meteorological Agency (JMA). analysis decay rates reveals a power-law time dependence scaling exponent close 1.0...

We use the back-projection method, with data recorded on dense USArray network, to estimate rupture propagation for Mw 9.0 earthquake that occurred offshore of Tohoku region, Japan. The results show a variable ranging from about 1.0 3.0 km/s high-frequency radiation. propagates over 450 km in approximately 150 s. Based speed and direction, source process can be divided into two parts. first part has relatively slow 1.5 northwestward. In second part, progresses southwestward starting...

Abstract The 2022 volcanic eruption in Tonga caused an unusually large tsunami around the Pacific. It travels with a faster apparent velocity and has larger amplitudes at long distances than what would be expected from conventional source. This was generated by moving atmospheric Lamb wave traveled speed of (0.31 km/s). Japanese data showed amplitude this first becomes small when approaching coast, due to weaker air‐sea coupling shallow depth. split passing continental slope, ocean gravity...

We study stress levels and radiated energy to infer the rupture characteristics scaling relationships of aftershocks other southern California earthquakes. use empirical Green functions obtain source time for 47 larger ( M ≥ 4.0) 1994 Northridge, earthquake 6.7). estimate static dynamic drops from compare them well‐calibrated estimates energy. Our measurements are relatively low compared drops, indicating that similar magnitude. This is confirmed by our direct drops. Combining results...

An unusually long (at least two hours) seismic wave train having periods of about 230 sec was recorded at many worldwide stations during the major eruption Mount Pinatubo in Philippines on June 15, 1991. This exhibits sharp spectral peaks 228 and 270 sec. The group velocity, phase particle motion this indicate that it is a Rayleigh wave. most probable excitation mechanism acoustic coupling atmospheric oscillations were set off by continuous thermal energy flux from volcano. correspond to...

We show the level of increased/decreased seismicity mapped across Japan immediately following 2003 Tokachi‐oki earthquake (M w 8.1) September 25, (UT) by use β‐statistic. Significant dynamic triggering events is found near Nankai subduction zone 900–1400 km from earthquake. The are inferred to be dynamically triggered deep low‐frequency earthquakes, a type that often occur in this region. appears caused long‐period oscillations surface waves, which may effective fluid‐related events. region...

We show that very large surface waves from the 2004 Sumatra‐Andaman earthquake (M9.2) triggered deep low‐frequency (DLF) seismic tremors beneath Japan over a 500 km wide region. The seismicity was periodically excited, synchronized with amplitudes and phases of oscillatory incident on Periodic excitation implies specific phase plays an important role for triggering. Estimation stress changes in source regions showed volumetric dilatation larger than ∼10 −8 predominant factor triggering,...

The Landers earthquake ( MW 7.3) of 28 June 1992 had a very emergent onset. first large amplitude arrivals are delayed by about 3 sec with respect to the origin time, and preceded smaller-scale slip. Other earthquakes have been observed similar onsets, but event is one be well recorded on nearby stations. We used these recordings investigate spatial relationship between hypocenter onset energy release, determine slip function 3-sec nucleation process. Relative location release initial...

[1] We carried out back-projections of teleseismic data filtered in different frequency bands for the 2010 Maule, Chile and 2011 Tohoku, Japan earthquakes. For Maule earthquake, there were differences along strike fault, with high-frequency energy mainly originating from an area 200 km northeast epicenter, whereas low-frequency came a location closer to epicenter. The Tohoku earthquake shows strong dependence dip direction. High-frequency sources located about 100 west while around near...

We perform a back projection method to image the rupture propagation and short‐period energy release of 2012 Off Northern Sumatra earthquake (M w 8.6) using Hi‐net data recorded in Japan. The results show complex pattern four conjugate faults over about 180 sec. There is striking correspondence between lengths orientations our with distribution aftershocks. Each first three stages corresponds clear lineation aftershocks, 200 400 km. Rupture speeds for several fault segments were very high, 5...