scholarly journals Travel times of principal P and S phases over small distances in southern California*

1944 ◽  
Vol 34 (1) ◽  
pp. 13-32
Author(s):  
B. Gutenberg
Keyword(s):  
Sierra Nevada ◽  
Southern California ◽  
Epicentral Distance ◽  
Focal Depth ◽  
Coastal Areas ◽  
Travel Times ◽  
Mountain Areas ◽  
Arrival Times ◽  
Order Of Magnitude ◽  
Characteristic Values

Summary Study of arrival times of the principal phases in fifty of the larger and better recorded earthquakes in southern California resulted in the following travel times t (seconds) and apparent velocities V (km/sec.): Pt = 0.1793DV = 5.577St = −0.5 + 0.3066DV = 3.26Pyt = 1.2+0.1654ΔV = 6.047Syt = 2.1 + 0.274ΔV = 3.65Pnt = x + 0.124ΔV = 8.06Snt = y + 0.225ΔV = 4.45 Δ = epicentral distance, D2 = Δ2 + h2, h = focal depth. x and y depend on the region; the following are characteristic values Coastal areas,Mountain areas,NorthernSierralow valleyssoutheastern Calif.Owens ValleyNevadax67910±sec.y8½9½12½14±sec. The average true velocities of Py and Sy are about one-third of one per cent, those of Pn and Sn about one-half of one per cent, smaller than the corresponding apparent velocities. In the uppermost 50 km. the velocity increases with depth. The order of magnitude of this increase is roughly 1 per cent per 10 kilometers, but larger in the uppermost one or two kilometers. It can be found from a study of amplitudes (Gutenberg, 1943c); its effect on the travel times exceeds the limits of error by too small an amount to be ascertained beyond doubt from the data of the present paper. The curvature of the earth can be disregarded within the range of distances used (in general not exceeding 800 km.). The effect of “mountain roots” on the travel times of Pn and Sn is investigated. Reproduction of travel-time curves and recalculation of the thickness of the various layers must wait until a study of other (especially reflected) recorded phases now under way is finished. Preliminary values are 18 km. for the thickness of the granitic layer with small local variations, and about 35 km. for the total of the crustal layers in the coastal areas of southern California with an increase inland approaching twice that amount under the Sierra Nevada.

An earthquake-explosion reversed refraction line in the Peninsular Ranges of southern California and Baja California Norte

1982 ◽  
Vol 72 (4) ◽  
pp. 1195-1206
Author(s):  
F. Alejandro Nava ◽  
James N. Brune
Keyword(s):  
Sierra Nevada ◽  
High Velocity ◽  
Southern California ◽  
Baja California ◽  
Crustal Thickness ◽  
Arrival Times ◽  
Narrow Zone ◽  
Peninsular Ranges ◽  
Thick Crust

abstract An approximate reversed refraction profile has been obtained for the center of the Peninsular Ranges of southern California and Baja California Norte using arrival times from Corona blasts to obtain the NW-SE profile, and arrival times from the well-located Pino Solo earthquake of 17 July 1975 to obtain the reversing SE-NW profile. The results indicate a relatively high-velocity crust, with P velocities of 6.57 to 6.95 km/sec, similar to the high velocities found by Hadley and Kanamori (1979). A crustal thickness of about 40 km was found for the axis of the Peninsular Ranges, significantly greater than was found by Hadley and Kanamori (1979) for the average crustal thickness of the northern part of the province. This suggests that the thick crust may be confined to a relatively narrow zone along the axis of the province. The crustal thickness found here is approximately 10 km less than found for the deeper crust of the Sierra Nevada (Bateman and Eaton, 1967; Pakiser and Brune, 1980).

Seismic velocity structure and event relocation in Kazakhstan from secondary P phases

1992 ◽  
Vol 82 (6) ◽  
pp. 2494-2510
Author(s):  
H. R. Quin ◽  
C. H. Thurber
Keyword(s):  
Velocity Structure ◽  
Seismic Velocity ◽  
Epicentral Distance ◽  
Focal Depth ◽  
Velocity Model ◽  
P Wave ◽  
Secondary Phases ◽  
Arrival Times ◽  
Event Location ◽  
Reflectivity Method

Abstract Three-component seismic data from a set of presumed explosions recorded by stations at Bayanaul and Karkaralinsk in Kazakhstan were analyzed in order to model the crustal structure of the region and to examine the use of the arrival times of secondary P phases, primarily PmP, in regional event location. Polarization analysis aided in the identification of the secondary phases. Low-pass filtered data (4-Hz corner) from the first 5 to 10 sec of 13 presumed explosions were modeled with the reflectivity method. The two chemical explosions in 1987 provided a check on accuracy, as their locations and origin times are accurately known. A good fit to the arrival times and amplitudes in the first 5 sec of the P wave (Pn, Pg, and PmP) was obtained in the epicentral distance range of 100 to 300 km. Beyond 300 km, the simple layered model was not adequate to model the PmP arrival. The crustal P-wave velocity model we derived has an upper crustal velocity increasing fairly rapidly from 4.5 km/sec near the surface to 6.5 km/sec at 15-km depth, then increasing more slowly to 7.05 km/sec at 50-km depth. The observed difference in the arrival times of the phases Pg, PmP, and Pn in the range between 100- and 250-km distance required a relatively sharp transition at the crust mantle boundary. The model is generally similar to previous estimates of P velocity structure in the region, though with a gentler gradient in the upper crust and a steeper gradient in the lower crust. We used the derived crustal model and the primary and secondary P-wave arrival times to relocate events in the Kazakhstan region. Inclusion of the phase PmP substantially decreases the focal depth uncertainty for many of the events. All but one of the events analyzed are concluded to be surface explosions; the identity of the remaining event is uncertain.

scholarly journals Travel times from blasts in southern California*

1951 ◽  
Vol 41 (1) ◽  
pp. 5-12 ◽  
Author(s):  
B. Gutenberg
Keyword(s):  
Southern California ◽  
Apparent Velocity ◽  
Travel Times ◽  
P Waves ◽  
Transverse Waves ◽  
Arrival Times ◽  
S Waves ◽  
Mohorovičić Discontinuity

abstract Seismograms recorded from a blast of about 70 tons of Du Pont “Nitramon” in tunnels at a quarry near Corona, southern California, are discussed. Arrival times of P waves indicate a velocity of between 5.7 and 6.0 km/sec. in the upper 6 km. of the region, and a velocity of about 6 1/2 km/sec. at a depth of 10 km. The Mohorovičić discontinuity is at a depth of the order of 40 km. The velocity below it is 8.1 to 8.2 km/sec. The amplitudes of S waves are only slightly more than one-tenth of those in an earthquake having P waves of equal amplitudes. The ratio of the velocity of P to that of the first recognizable S is found between 1.6 and 1.7. The first S waves at distances up to about 140 km. indicate a velocity of transverse waves of about 3¾ km/sec. at a depth of the order of 10 km. A phase with an apparent velocity of about 3 1/2 km/sec. can be traced to more than 400 km. It is followed by several slower phases. On the assumption that the amplitudes of Pn do not differ appreciably from those in an earthquake of the same magnitude, the blast would have had a magnitude of about 4.

Velocity of elastic waves and structure of the crust in the vicinity of Ottawa, Canada*

1942 ◽  
Vol 32 (4) ◽  
pp. 249-255
Author(s):  
Ernest A. Hodgson
Keyword(s):  
Elastic Waves ◽  
Single Point ◽  
Focal Depth ◽  
The Other ◽  
Northern Europe ◽  
Earth Structure ◽  
Travel Times ◽  
Arrival Times ◽  
The Earth ◽  
Mohorovičić Discontinuity

Summary Ten seismograms, due to rockbursts at Lake Shore Mines, Kirkland Lake, Ontario, were recorded on a Benioff seismograph at Ottawa at a distance of 450 km. (279 mi.). The center of each burst was located within a few feet; but, for the purpose of preparing travel-time tables, they may all be considered to have occurred at a single point at the surface. Two of the bursts were accurately timed on the seismograph at the mine. Six phases were registered on each seismogram, being more sharply marked on some records than on others. Five of these are well defined on nearly all the records. It is thus possible to deduce a set of arrival times at a distance of 450 km. for a burst (or earthquake) occurring at the surface; and this set of times is known with fair precision, since all the readings may be combined. The distance is determined within one part in 7000, the depth within 2000 ft. and the travel times with an error of ±.5 sec. These travel times have been compared with those obtained by Joliat in computing his Tables for Near Earthquakes, based on the velocities deduced by Jeffreys for northern Europe and arbitrarily assuming an earth structure with two layers above the Mohorovičić discontinuity. The differences are minor and are to be explained as chiefly owing to the fact that Joliat assumed the focus to lie at the bottom instead of the top of the upper layer. On the strength of the comparisons afforded by the ten seismograms, the focal time of each burst may be considered as known within ±.5 sec. One of the bursts was so severe that it was registered also at Shawinigan Falls, Quebec (Δ = 576 km., 358 mi.) and at Weston, Massachusetts (Δ = 935 km., 581 mi.). These records will afford a means of deducing the earth structure and velocities in the vicinity of Ottawa, and will permit the construction of tables for rock-bursts and blasts in that area up to 10° (1110 km., 690 mi.). These will be prepared and issued, together with corrections permitting their being used for local earthquakes with finite focal depth. Should other bursts occur later at Kirkland Lake, timed by the mine seismograph and registered at Ottawa or the other stations, the data so made available may be directly used to check and add precision to the deductions made from the seismograms already in hand. Such further data would be most valuable.

scholarly journals Near-surface real-time seismic imaging using parsimonious interferometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sherif M. Hanafy ◽  
Hussein Hoteit ◽  
Jing Li ◽  
Gerard T. Schuster
Keyword(s):  
Fluid Flow ◽  
Real Time ◽  
Temporal Resolution ◽  
Seismic Imaging ◽  
Time Lapse ◽  
Rock Properties ◽  
Recording Time ◽  
Near Surface ◽  
Arrival Times ◽  
Order Of Magnitude

AbstractResults are presented for real-time seismic imaging of subsurface fluid flow by parsimonious refraction and surface-wave interferometry. Each subsurface velocity image inverted from time-lapse seismic data only requires several minutes of recording time, which is less than the time-scale of the fluid-induced changes in the rock properties. In this sense this is real-time imaging. The images are P-velocity tomograms inverted from the first-arrival times and the S-velocity tomograms inverted from dispersion curves. Compared to conventional seismic imaging, parsimonious interferometry reduces the recording time and increases the temporal resolution of time-lapse seismic images by more than an order-of-magnitude. In our seismic experiment, we recorded 90 sparse data sets over 4.5 h while injecting 12-tons of water into a sand dune. Results show that the percolation of water is mostly along layered boundaries down to a depth of a few meters, which is consistent with our 3D computational fluid flow simulations and laboratory experiments. The significance of parsimonious interferometry is that it provides more than an order-of-magnitude increase of temporal resolution in time-lapse seismic imaging. We believe that real-time seismic imaging will have important applications for non-destructive characterization in environmental, biomedical, and subsurface imaging.

scholarly journals Formation Patterns of Mediterranean High-Mountain Water-Bodies in Sierra-Nevada, SE Spain

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 438
Author(s):  
Jose Luis Diaz-Hernandez ◽  
Antonio Jose Herrera-Martinez
Keyword(s):  
Sierra Nevada ◽  
Unknown Origin ◽  
Slope Instability ◽  
Water Bodies ◽  
High Mountain ◽  
Mountain Areas ◽  
Glacial Processes ◽  
The Mediterranean ◽  
Water Volumes

At present, there is a lack of detailed understanding on how the factors converging on water variables from mountain areas modify the quantity and quality of their watercourses, which are features determining these areas’ hydrological contribution to downstream regions. In order to remedy this situation to some extent, we studied the water-bodies of the western sector of the Sierra Nevada massif (Spain). Since thaw is a necessary but not sufficient contributor to the formation of these fragile water-bodies, we carried out field visits to identify their number, size and spatial distribution as well as their different modelling processes. The best-defined water-bodies were the result of glacial processes, such as overdeepening and moraine dams. These water-bodies are the highest in the massif (2918 m mean altitude), the largest and the deepest, making up 72% of the total. Another group is formed by hillside instability phenomena, which are very dynamic and are related to a variety of processes. The resulting water-bodies are irregular and located at lower altitudes (2842 m mean altitude), representing 25% of the total. The third group is the smallest (3%), with one subgroup formed by anthropic causes and another formed from unknown origin. It has recently been found that the Mediterranean and Atlantic watersheds of this massif are somewhat paradoxical in behaviour, since, despite its higher xericity, the Mediterranean watershed generally has higher water contents than the Atlantic. The overall cause of these discrepancies between watersheds is not connected to their formation processes. However, we found that the classification of water volumes by the manners of formation of their water-bodies is not coherent with the associated green fringes because of the anomalous behaviour of the water-bodies formed by moraine dams. This discrepancy is largely due to the passive role of the water retained in this type of water-body as it depends on the characteristics of its hollows. The water-bodies of Sierra Nevada close to the peak line (2918 m mean altitude) are therefore highly dependent on the glacial processes that created the hollows in which they are located. Slope instability created water-bodies mainly located at lower altitudes (2842 m mean altitude), representing tectonic weak zones or accumulation of debris, which are influenced by intense slope dynamics. These water-bodies are therefore more fragile, and their existence is probably more short-lived than that of bodies created under glacial conditions.

A method of obtaining P and S travel-time curves within a “Stripped Earth”*

1952 ◽  
Vol 42 (4) ◽  
pp. 313-314
Author(s):  
V. C. Stechschulte
Keyword(s):  
Travel Time ◽  
Depth Distribution ◽  
Epicentral Distance ◽  
Travel Times ◽  
Depth Of Focus ◽  
Distance Curve ◽  
Simple Method ◽  
Time Distance ◽  
Deep Focus

Abstract A simple method is outlined for obtaining from a time-distance curve of a deep-focus earthquake a table of travel times within an earth “stripped” to the depth h, the depth of focus. The method depends on the fact that such a curve for a deep-focus earthquake has a point of inflection and therefore has the same slope at two different values of epicentral distance. The Herglotz-Wiechert method may then be applied to these travel times to obtain a velocity-depth distribution.

Shear velocity from differential travel times of short-period ScS-P in New Hebrides, Fiji-Tonga, and Banda Sea regions

1975 ◽  
Vol 65 (6) ◽  
pp. 1787-1796
Author(s):  
Mansur A. Choudhury ◽  
Georges Poupinet ◽  
Guy Perrier
Keyword(s):  
Upper Mantle ◽  
Focal Depth ◽  
Shear Velocity ◽  
Mean Value ◽  
Travel Times ◽  
Velocity Models ◽  
Depth Dependence ◽  
Short Period ◽  
New Hebrides ◽  
The Antarctic

abstract Behavior of P, S and ScS residuals as well as those of differential travel times of ScS-P from the Jeffreys-Bullen tables are analyzed. The phases have been read from short-period records of the Antarctic station, Dumont d'Urville (DRV); the earthquakes originating in New Hebrides, Fiji-Tonga, and Banda Sea regions. P residuals from all regions show a mean value of about −1 sec. On the contrary, S and ScS residuals, well correlated among themselves, show important regional as well as focal-depth dependence. ScS-P residuals from shallow and intermediate shocks are largely positive for New Hebrides and largely negative for Banda Sea; those from intermediate shocks are moderately positive for Fiji-Tonga. The anomalies disappear at depths greater than about 200 km. Upper mantle shear velocity models are presented for the three regions. The models are discussed in relation to a sinking lithosphere.

The Hindu Kush earthquake of March 4, 1949 as recorded in Europe

1964 ◽  
Vol 54 (6A) ◽  
pp. 1915-1925 ◽  
Author(s):  
I. Lehmann
Keyword(s):  
Amplitude Ratio ◽  
Epicentral Distance ◽  
Focal Region ◽  
Travel Times ◽  
Period Range ◽  
Characteristic Appearance ◽  
Hindu Kush ◽  
The Difference ◽  
Deep Focus ◽  
The Many

abstract The European records from distances 36°-50° of the deep Hindu Kush earthquake of March 4, 1949 were studied. The many clearly recorded deep-focus reflections lend to the records a characteristic appearance which is repeated in many other shocks from the same focal region. The ratios of the amplitudes of these phases vary somewhat from one shock to another. In the shock here considered sP and sPP are exceptionally large at most stations; in the Italian stations they are not so large, while pP is a clear phase. pP is not very well defined at most other stations. Most of the 1949 records were from the old type long-period instruments having their highest magnification for periods from about 5 sec to 12 sec. Present day instruments of quite short or of very long proper period while admirable for many purposes do not record waves in this period range very well and therefore do not produce a satisfactory picture of the forerunners of earthquakes. The difference between the records obtained on different instruments is illustrated. It is shown in examples that the amplitude ratio PP:P may differ strongly at the same epicentral distance and also that pP may vary greatly with azimuth. The deficiency of station readings is noted. Travel times and their residuals are tabulated and travel times plotted versus epicentral distances.

scholarly journals Wave velocities in the earth's core

1958 ◽  
Vol 48 (4) ◽  
pp. 301-314
Author(s):  
B. Gutenberg
Keyword(s):  
Travel Time ◽  
Transition Zone ◽  
Southern California ◽  
Inner Core ◽  
Travel Times ◽  
Earth’S Core ◽  
Earth's Core ◽  
The Core ◽  
Wave Velocities

Abstract More than 700 seismograms of 39 shocks recorded mainly in southern California at epicentral distances between 105 and 140 degrees are used to investigate records of phases which have penetrated the earth's core. Properties of PKIKP, SKP, SKIKP, PKS, and PKIKS are discussed. Portions of travel-time curves of these phases are revised. Travel times of waves starting and ending at the surface of the core, and wave velocities in the core, are recalculated. Between about 1,500 and 1,200 km. from the earth's center in the transition zone from the liquid outer to the probably solid inner core, waves having lengths of the order of 10 km. travel faster than longer waves. This is probably caused by a rather rapid increase in viscosity toward the earth's center in this transition zone.

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