James Jackson - Academia.edu (original) (raw)
Papers by James Jackson
Earth and Planetary Science Letters, 1983
The deformation of continental lithosphere generally does not occur on a single fault, but is dis... more The deformation of continental lithosphere generally does not occur on a single fault, but is distributed over a zone up to a few hundred kilometers wide. If the deformation rate is constant throughout the zone, and if the velocity is continuous everywhere and does not change with time, the deformation gradient tensor can be obtained analytically. This tensor directly determines the amount of crustal thickening, and is related in a complicated manner to the finite strain tensor. The declination of remnant magnetization, measured within the zone, can also be rotated by the deformation. Because palaeomagnetic measurements are generally made on rigid blocks which have not been deformed, there is no simple relationship between such rotations and the finite strain. Expressions for all these quantities are obtained in terms of the velocity gradients, which are taken to be constant. The history of western North America is used to illustrate the relationship between the present deformation by strike slip and thrust motions, the rotations of the remnant magnetization vectors and the shape of accreted terranes.
Geophysical Journal International, 1984
Over 80 new fault plane solutions, combined with satellite imagery as well as both modern and his... more Over 80 new fault plane solutions, combined with satellite imagery as well as both modern and historical observations of earthquake faulting, are used to investigate the active tectonics of the Middle East between western Turkey and Pakistan.The deformation of the western part of this region is dominated by the movement of continental material laterally away from the Lake Van region in eastern Turkey. This movement helps to avoid crustal thickening in the Van region, and allows some of the shortening between Arabia and Eurasia to be taken up by the thrusting of continental material over oceanic-type basement in the southern Caspian, Mediterranean, Makran and Black Sea. Thus central Turkey, bounded by the North and East Anatolian strike-slip faults, is moving west from the Van region and overrides the eastern Mediterranean at two intermediate depth seismic zones: one extending between Antalya Bay and southern Cyprus, and the other further west in the Hellenic Trench. The motion of northern Iran eastwards from the Van region is achieved mainly by a conjugate system of strike-slip faults and leads to the low angle thrusting of Iran over the southern Caspian Sea. The seismicity of the Caucasus shows predominantly shortening perpendicular to the regional strike, but there is also some minor elongation along the strike of the belt as the Causcasus overrides the Caspian and Black Seas.The deformation of the eastern part of this region is dominated by the shortening of Iran against the stable borders of Turkmenistan and Afghanistan. The north-east direction of compression seen in Zagros is also seen in north-east Iran and the Kopet Dag, where the shortening is taken up by a combination of strike-slip and thrust faulting. Large structural as well as palaeomagnetic rotations are likely to have occurred in NE Iran as a result of this style of deformation. North-south strike-slip faults in southern Iran allow some movement of material away from the collision zone in NE Iran towards the Makran subduction zone, where genuinely intermediate depth seismicity is seen.Within this broad deforming belt large areas, such as central Turkey, NW Iran (Azerbaijan), central Iran and the southern Caspian, appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200-300 km wide. The motion of these blocks can usefully be described by poles of rotation. The poles presented in this paper predict motions consistent with those observed and also predict the opening of the Gulf of Iskenderun NE of Cyprus, the change within the Zagros mountains from strike-slip faulting in the NW to intense thrusting in the SE, and the relatively feeble seismicity in SE Iran (Baluchistan). This description also explains why the north-south structures along the Iran-Afghanistan border do not cut the east-west ranges of the Makran.Within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation, even though motions at the surface may be concentrated on faults. The evolution of fault systems within the active zones is controlled by geometric constraints, such as the requirement that simultaneously active faults do not, in general, intersect.Many of the active processes discussed in this paper, particularly large-scale rotations and lateral movement along the regional strike, are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them.
Annual Review of Earth and Planetary Sciences, 1994
... This review summarizes what we expect these new techniques to be able to see, the extent to w... more ... This review summarizes what we expect these new techniques to be able to see, the extent to which early geodetic results are compatible with the nongeodetic estimates, and the insight these studies give into the ... Figure 9 shows a velocity field in the Aegean obtained by ...
Geophysical Journal International, 1991
In this paper we examine the connection between the westward motion of Turkey relative to Europe ... more In this paper we examine the connection between the westward motion of Turkey relative to Europe and the extension in and around the Aegean Sea. The principal new data available since the last attempt to synthesize the tectonics of this region by McKenzie (1978) are much improved focal mechanisms of earthquakes, constrained by P and SH body wave modelling as well as by first motions. These mechanisms show that the faulting in the western part of the Aegean region is mostly extensional in nature, on normal faults with a NW to WNW strike and with slip vectors directed NNW to NNE. There is evidence from palaeomagnetism that this western region rotates clockwise relative to stable Europe. In the central and eastern Aegean, and in NW Turkey, distributed right-lateral strike–slip is more prevalent, on faults trending NE to ENE, and with slip vectors directed NE. Palaeomagnetic data in this eastern region is more ambiguous, but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations, relative to Europe, in the south. The strike–slip faulting that enters the central Aegean from the east appears to end abruptly in the SW against the NW-trending normal faults of Greece.The kinematics of the deformation is controlled by three factors: the westward motion of Turkey relative to Europe; the continental collision between NW Greece–Albania and the Apulia–Adriatic platform in the west; and the presence of the Hellenic subduction zone to the south. As the right-lateral slip on the North Anatolian Fault enters the Aegean region it splays out, becoming distributed on several parallel faults. The continental shortening in NW Greece and Albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed E–W right-lateral shear, and thus leads to E–W shortening in the northern Aegean, which is compensated by N–S extension as the southern Aegean margin can move easily over the Hellenic subduction zone. The dynamics of the system, once initiated, is self-sustaining, being driven by the high topography in eastern Turkey and by the roll-back of the subducted slab beneath the southern Aegean.The geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate. In spite of its extreme simplicity, a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the Aegean region, including: the slip vectors and nature of the faulting in the eastern and western parts; the senses and approximate rates of rotation; the overall extensional velocity across the Aegean; and the distribution of strain rates, as seen in the seismicity and topography or bathymetry, and using geodetic measurements.As part of this study, we re-examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 Gulf of Corinth earthquakes, and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting. An important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves.
Geophysical Journal International, 1991
The East Anatolian Fault Zone accommodates most of the motion between the Arabian plate and the a... more The East Anatolian Fault Zone accommodates most of the motion between the Arabian plate and the apparently little-deforming interior of central Turkey. The direction of overall slip across this zone is crucial to the determination of the slip rate on the North Anatolian Fault. We use long-period P- and SH-waveforms to determine the source parameters of the four largest earthquakes that occurred in, or near, the East Anatolian Fault Zone in the last 35 years. Only one of these actually involved left-lateral strike–slip motion on a NE–SW fault. But the other three, and the nearby 1975 Lice earthquake, all had steeply dipping nodal planes with a NNW strike: if these were the auxiliary planes then all the earthquakes had a slip vector direction within about 10° of 063°. If this direction represents the Arabia–Turkey motion, then the slip rate on the North Anatolian Fault must be in the range 31 to 48 mm yr−1, with a probable value of 38 mm yr−1, and the overall slip rate across the East Anatolian Fault Zone must be about 29 mm yr−1 with a range of 25–35 mm yr−1.
Molecular Cell, 2000
Genetics of the involved genes are allowing a molecular interpre-Wageningen University tation of ... more Genetics of the involved genes are allowing a molecular interpre-Wageningen University tation of these pathways. However, the available infor-Dreijenlaan 2 mation is fragmented, and many aspects of this develop-6703 HA Wageningen mental process remain poorly understood. The Netherlands One of the factors suggested to play a role in the † Department of MCD Biology regulation of gene expression affecting flowering transi-University of California, Los Angeles tion is DNA methylation (Finnegan et al., 2000). The ac-Los Angeles, California 90095 tual significance of DNA methylation for gene regulation ‡ National Institute of Genetics in plant development remains unknown. An overall re-Yata 1111 duction in total genomic cytosine methylation of up to Mishima, Shizuoka 411-8540 70% has been found in transgenic plants with reduced Japan amounts of DNA methyltransferase (Finnegan et al., 1996; Ronemus et al., 1996) and in decrease in DNA methylation (ddm1) mutant plants that are defective in Summary a protein that is likely to be involved in chromatin remodeling (Jeddeloh et al., 1999). Such plants develop a num-The transition to flowering in Arabidopsis thaliana is ber of phenotypic abnormalities (Vongs et al., 1993; Findelayed in fwa mutant plants. FWA was identified by negan et al., 1996; Kakutani et al., 1996; Ronemus et loss-of-function mutations in normally flowering real., 1996). Furthermore, it has been observed that stable vertants of the fwa mutant, and it encodes a homeodoenhancement of the methylation level in specific genes main-containing transcription factor. The DNA secan suppress expression of these genes, leading to muquence of wild-type and fwa mutant alleles was tant phenotypes (Jacobsen and Meyerowitz, 1997; Cuidentical in the genomic region of FWA. Furthermore, bas et al., 1999; Jacobsen et al., 2000). the FWA gene is ectopically expressed in fwa mutants In relation to flowering, experimental arguments supand silenced in mature wild-type plants. This silencing porting a role for DNA methylation are largely correlative is associated with extensive methylation of two direct (Finnegan et al., 1998). For instance, Arabidopsis plants repeats in the 5 region of the gene. The late flowering that are exposed to low temperatures during a prophenotype, ectopic FWA expression, and hypomethyllonged period (vernalization), and plants that are treated with the DNA demethylating agent 5-azacytidine show ation of the repeats were also induced in the ddm1 reduced levels of 5-methylcytosine and early flowering hypomethylated background. Mechanisms for estabas compared to untreated plants (Burn et al., 1993). lishment and maintenance of the epigenetic mark on Thus, it has been hypothesized that vernalization pro-FWA are discussed. motes flowering through demethylation of the genome. Apart from early flowering plants, late flowering plants Introduction were derived from the hypomethylated backgrounds of antisense DNA methyltransferase (as-MET1) (Ronemus Induction of flowering at the appropriate moment is eset al., 1996) and ddm1 (Kakutani . Therefore, sential for many plant species to reproduce successcontrasting phenotypes have been related to altering fully. The fine tuning of the transition from the vegetative methylation, suggesting that multiple genes with oppoto the reproductive phase is believed to be under control site effects might be involved in the epigenetic regulaof multiple factors. These are both endogenous, such tion of flowering. Nevertheless, to prove and understand as gibberellins and carbohydrate metabolites, and envithe involvement of such mechanisms awaits the identifironmental, such as day length, temperature, and light cation of target genes that are affected directly by methquality. To understand this process, a genetic approach ylation. is underway in Arabidopsis in which a multitude of mu-
Nature, 2002
In vitro growth assay Cells were seeded in triplicate in 12-well plates at a concentration of 3 £... more In vitro growth assay Cells were seeded in triplicate in 12-well plates at a concentration of 3 £ 10 4 cells per well. Cells were collected at days 2, 4, 6 and 8, and viable cells, as assessed by trypan blue exclusion, were counted in a haemocytometer.
Naval Research Logistics Quarterly, 1956
Johnson's method for efficiently solving certaintwo-stage production scheduling problems is gener... more Johnson's method for efficiently solving certaintwo-stage production scheduling problems is generalized to include cases in which some jobs require only a single stage and in which the two-stage jobs may require the machines in both of the possible orders.
Earth and Planetary Science Letters, 1983
The deformation of continental lithosphere generally does not occur on a single fault, but is dis... more The deformation of continental lithosphere generally does not occur on a single fault, but is distributed over a zone up to a few hundred kilometers wide. If the deformation rate is constant throughout the zone, and if the velocity is continuous everywhere and does not change with time, the deformation gradient tensor can be obtained analytically. This tensor directly determines the amount of crustal thickening, and is related in a complicated manner to the finite strain tensor. The declination of remnant magnetization, measured within the zone, can also be rotated by the deformation. Because palaeomagnetic measurements are generally made on rigid blocks which have not been deformed, there is no simple relationship between such rotations and the finite strain. Expressions for all these quantities are obtained in terms of the velocity gradients, which are taken to be constant. The history of western North America is used to illustrate the relationship between the present deformation by strike slip and thrust motions, the rotations of the remnant magnetization vectors and the shape of accreted terranes.
Geophysical Journal International, 1984
Over 80 new fault plane solutions, combined with satellite imagery as well as both modern and his... more Over 80 new fault plane solutions, combined with satellite imagery as well as both modern and historical observations of earthquake faulting, are used to investigate the active tectonics of the Middle East between western Turkey and Pakistan.The deformation of the western part of this region is dominated by the movement of continental material laterally away from the Lake Van region in eastern Turkey. This movement helps to avoid crustal thickening in the Van region, and allows some of the shortening between Arabia and Eurasia to be taken up by the thrusting of continental material over oceanic-type basement in the southern Caspian, Mediterranean, Makran and Black Sea. Thus central Turkey, bounded by the North and East Anatolian strike-slip faults, is moving west from the Van region and overrides the eastern Mediterranean at two intermediate depth seismic zones: one extending between Antalya Bay and southern Cyprus, and the other further west in the Hellenic Trench. The motion of northern Iran eastwards from the Van region is achieved mainly by a conjugate system of strike-slip faults and leads to the low angle thrusting of Iran over the southern Caspian Sea. The seismicity of the Caucasus shows predominantly shortening perpendicular to the regional strike, but there is also some minor elongation along the strike of the belt as the Causcasus overrides the Caspian and Black Seas.The deformation of the eastern part of this region is dominated by the shortening of Iran against the stable borders of Turkmenistan and Afghanistan. The north-east direction of compression seen in Zagros is also seen in north-east Iran and the Kopet Dag, where the shortening is taken up by a combination of strike-slip and thrust faulting. Large structural as well as palaeomagnetic rotations are likely to have occurred in NE Iran as a result of this style of deformation. North-south strike-slip faults in southern Iran allow some movement of material away from the collision zone in NE Iran towards the Makran subduction zone, where genuinely intermediate depth seismicity is seen.Within this broad deforming belt large areas, such as central Turkey, NW Iran (Azerbaijan), central Iran and the southern Caspian, appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200-300 km wide. The motion of these blocks can usefully be described by poles of rotation. The poles presented in this paper predict motions consistent with those observed and also predict the opening of the Gulf of Iskenderun NE of Cyprus, the change within the Zagros mountains from strike-slip faulting in the NW to intense thrusting in the SE, and the relatively feeble seismicity in SE Iran (Baluchistan). This description also explains why the north-south structures along the Iran-Afghanistan border do not cut the east-west ranges of the Makran.Within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation, even though motions at the surface may be concentrated on faults. The evolution of fault systems within the active zones is controlled by geometric constraints, such as the requirement that simultaneously active faults do not, in general, intersect.Many of the active processes discussed in this paper, particularly large-scale rotations and lateral movement along the regional strike, are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them.
Annual Review of Earth and Planetary Sciences, 1994
... This review summarizes what we expect these new techniques to be able to see, the extent to w... more ... This review summarizes what we expect these new techniques to be able to see, the extent to which early geodetic results are compatible with the nongeodetic estimates, and the insight these studies give into the ... Figure 9 shows a velocity field in the Aegean obtained by ...
Geophysical Journal International, 1991
In this paper we examine the connection between the westward motion of Turkey relative to Europe ... more In this paper we examine the connection between the westward motion of Turkey relative to Europe and the extension in and around the Aegean Sea. The principal new data available since the last attempt to synthesize the tectonics of this region by McKenzie (1978) are much improved focal mechanisms of earthquakes, constrained by P and SH body wave modelling as well as by first motions. These mechanisms show that the faulting in the western part of the Aegean region is mostly extensional in nature, on normal faults with a NW to WNW strike and with slip vectors directed NNW to NNE. There is evidence from palaeomagnetism that this western region rotates clockwise relative to stable Europe. In the central and eastern Aegean, and in NW Turkey, distributed right-lateral strike–slip is more prevalent, on faults trending NE to ENE, and with slip vectors directed NE. Palaeomagnetic data in this eastern region is more ambiguous, but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations, relative to Europe, in the south. The strike–slip faulting that enters the central Aegean from the east appears to end abruptly in the SW against the NW-trending normal faults of Greece.The kinematics of the deformation is controlled by three factors: the westward motion of Turkey relative to Europe; the continental collision between NW Greece–Albania and the Apulia–Adriatic platform in the west; and the presence of the Hellenic subduction zone to the south. As the right-lateral slip on the North Anatolian Fault enters the Aegean region it splays out, becoming distributed on several parallel faults. The continental shortening in NW Greece and Albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed E–W right-lateral shear, and thus leads to E–W shortening in the northern Aegean, which is compensated by N–S extension as the southern Aegean margin can move easily over the Hellenic subduction zone. The dynamics of the system, once initiated, is self-sustaining, being driven by the high topography in eastern Turkey and by the roll-back of the subducted slab beneath the southern Aegean.The geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate. In spite of its extreme simplicity, a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the Aegean region, including: the slip vectors and nature of the faulting in the eastern and western parts; the senses and approximate rates of rotation; the overall extensional velocity across the Aegean; and the distribution of strain rates, as seen in the seismicity and topography or bathymetry, and using geodetic measurements.As part of this study, we re-examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 Gulf of Corinth earthquakes, and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting. An important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves.
Geophysical Journal International, 1991
The East Anatolian Fault Zone accommodates most of the motion between the Arabian plate and the a... more The East Anatolian Fault Zone accommodates most of the motion between the Arabian plate and the apparently little-deforming interior of central Turkey. The direction of overall slip across this zone is crucial to the determination of the slip rate on the North Anatolian Fault. We use long-period P- and SH-waveforms to determine the source parameters of the four largest earthquakes that occurred in, or near, the East Anatolian Fault Zone in the last 35 years. Only one of these actually involved left-lateral strike–slip motion on a NE–SW fault. But the other three, and the nearby 1975 Lice earthquake, all had steeply dipping nodal planes with a NNW strike: if these were the auxiliary planes then all the earthquakes had a slip vector direction within about 10° of 063°. If this direction represents the Arabia–Turkey motion, then the slip rate on the North Anatolian Fault must be in the range 31 to 48 mm yr−1, with a probable value of 38 mm yr−1, and the overall slip rate across the East Anatolian Fault Zone must be about 29 mm yr−1 with a range of 25–35 mm yr−1.
Molecular Cell, 2000
Genetics of the involved genes are allowing a molecular interpre-Wageningen University tation of ... more Genetics of the involved genes are allowing a molecular interpre-Wageningen University tation of these pathways. However, the available infor-Dreijenlaan 2 mation is fragmented, and many aspects of this develop-6703 HA Wageningen mental process remain poorly understood. The Netherlands One of the factors suggested to play a role in the † Department of MCD Biology regulation of gene expression affecting flowering transi-University of California, Los Angeles tion is DNA methylation (Finnegan et al., 2000). The ac-Los Angeles, California 90095 tual significance of DNA methylation for gene regulation ‡ National Institute of Genetics in plant development remains unknown. An overall re-Yata 1111 duction in total genomic cytosine methylation of up to Mishima, Shizuoka 411-8540 70% has been found in transgenic plants with reduced Japan amounts of DNA methyltransferase (Finnegan et al., 1996; Ronemus et al., 1996) and in decrease in DNA methylation (ddm1) mutant plants that are defective in Summary a protein that is likely to be involved in chromatin remodeling (Jeddeloh et al., 1999). Such plants develop a num-The transition to flowering in Arabidopsis thaliana is ber of phenotypic abnormalities (Vongs et al., 1993; Findelayed in fwa mutant plants. FWA was identified by negan et al., 1996; Kakutani et al., 1996; Ronemus et loss-of-function mutations in normally flowering real., 1996). Furthermore, it has been observed that stable vertants of the fwa mutant, and it encodes a homeodoenhancement of the methylation level in specific genes main-containing transcription factor. The DNA secan suppress expression of these genes, leading to muquence of wild-type and fwa mutant alleles was tant phenotypes (Jacobsen and Meyerowitz, 1997; Cuidentical in the genomic region of FWA. Furthermore, bas et al., 1999; Jacobsen et al., 2000). the FWA gene is ectopically expressed in fwa mutants In relation to flowering, experimental arguments supand silenced in mature wild-type plants. This silencing porting a role for DNA methylation are largely correlative is associated with extensive methylation of two direct (Finnegan et al., 1998). For instance, Arabidopsis plants repeats in the 5 region of the gene. The late flowering that are exposed to low temperatures during a prophenotype, ectopic FWA expression, and hypomethyllonged period (vernalization), and plants that are treated with the DNA demethylating agent 5-azacytidine show ation of the repeats were also induced in the ddm1 reduced levels of 5-methylcytosine and early flowering hypomethylated background. Mechanisms for estabas compared to untreated plants (Burn et al., 1993). lishment and maintenance of the epigenetic mark on Thus, it has been hypothesized that vernalization pro-FWA are discussed. motes flowering through demethylation of the genome. Apart from early flowering plants, late flowering plants Introduction were derived from the hypomethylated backgrounds of antisense DNA methyltransferase (as-MET1) (Ronemus Induction of flowering at the appropriate moment is eset al., 1996) and ddm1 (Kakutani . Therefore, sential for many plant species to reproduce successcontrasting phenotypes have been related to altering fully. The fine tuning of the transition from the vegetative methylation, suggesting that multiple genes with oppoto the reproductive phase is believed to be under control site effects might be involved in the epigenetic regulaof multiple factors. These are both endogenous, such tion of flowering. Nevertheless, to prove and understand as gibberellins and carbohydrate metabolites, and envithe involvement of such mechanisms awaits the identifironmental, such as day length, temperature, and light cation of target genes that are affected directly by methquality. To understand this process, a genetic approach ylation. is underway in Arabidopsis in which a multitude of mu-
Nature, 2002
In vitro growth assay Cells were seeded in triplicate in 12-well plates at a concentration of 3 £... more In vitro growth assay Cells were seeded in triplicate in 12-well plates at a concentration of 3 £ 10 4 cells per well. Cells were collected at days 2, 4, 6 and 8, and viable cells, as assessed by trypan blue exclusion, were counted in a haemocytometer.
Naval Research Logistics Quarterly, 1956
Johnson's method for efficiently solving certaintwo-stage production scheduling problems is gener... more Johnson's method for efficiently solving certaintwo-stage production scheduling problems is generalized to include cases in which some jobs require only a single stage and in which the two-stage jobs may require the machines in both of the possible orders.