Advances in Planetary Seismology Using Infrasound and ... · Aug 15 to 17, 2017 LCPM-12 Conference, Pasadena, CA 1 Advances in Planetary Seismology Using Infrasound and Airglow Signatures

Aug 15 to 17, 2017 1LCPM-12 Conference, Pasadena, CA

Advances in Planetary Seismology Using

Infrasound and Airglow Signatures on

Venus

1JPL/Caltech; 2Caltech, Pasadena, CA, USA; 3ISAE, Toulouse; France 4IPGP, Paris, France

Email: [email protected]

1Attila Komjathy, 1Siddharth Krishnamoorthy 1James Cutts, 1Michael Pauken,, 1Sharon Kedar, 1Suzanne Smrekar, 1Jeff

Hall, 1Alan Didion, 1Balthasar Kenda, 1Xing Meng, 1Olga Verkhoglyadova, 1Walton Williamson, 2Jennifer Jackson, 3David Mimoun, 3Raphael Garcia and 4Philippe Lognonné

mailto:[email protected]


Introduction

• Motivation

• Balloon infrasound technique for Venus

• Earth-based experience

• Modeling background on Earth

• Planned Phase 1 to 3 experiments on Earth

• Airglow measurements on Venus

• Conclusions

• Acknowledgements


Motivation

• The planetary evolution and structure of Venus remain uncertain more than half a century after the first visit by a robotic spacecraft.

• To understand how Venus evolved it is necessary to detect the signs of seismic activity.

• Due to the adverse surface conditions on Venus, with extremely high temperature and pressure, it is infeasible to place seismometers on the surface for an extended period of time.

• Due to dynamic coupling between the solid planet and the atmosphere, the waves generated by quakes propagate and can be detected in the atmosphere itself.

• Our goals are:

• Detect seismicity using infrasound measurements and characterize seismic wave propagation in order to determine crustal structure

• Conduct complementary investigation of airglow phenomenology, atmospheric gravity waves and ionospheric disturbances


Three Techniques Defined at KISS Workshop at Caltech to Detect Seismicity on Venus

2)

Airglow

imaging

from

orbit

1)

Infrasound

observation

s at 55km

and -10

°C

2) Classical

seismic

measurements

with surface temp

of 465 °C

1) Infrasound measurements

2) Airglow imaging and 3) Seismometer on ground (currently

infeasible).


Earth: Generation of Infrasound by Quakes

• Earthquakes and

volcanoes on Earth

can be detected using

infrasound techniques

in situ or from space

• Measuring and

modeling techniques

of infrasound signals

on Earth are well

understood


Venus Epicentral and RayleighInfrasound Waves

60km

150km

Venus: Epicentral

Infrasound

Secondary Rayleigh

Infrasound• Seismic signals

couple 60X more

efficiently into the

atmosphere on Venus

than on Earth

• Infrasound wave

replicas of seismic

waves are near

perfect

• Almost no attenuation

below 80 km for

frequency < 1Hz,

hence use balloons


Completed Aerostat Experiment: Altitude

Up to 1300 Feet on June 28, 2017

Infrasound signatures associated

with Rayleigh waves

Source: Seismic hammer

Objective:

Detect highly reproducible signal

Benefit: Validate 2-barometer

signal processing using point

source

Barometer 1

Barometer 2

(photos of actual experiment)


Altitude

Phase 1

Balloon

Climbing

Phase 2

Tether / Baro

Deployment

Phase 3

MeasurementPhase 4

Tether / Baro

withdrawal

Time

T≃2-3 hours

Hmax< 1 km

Seismic hammer with the hot air

balloon monitoring ground strikes

Completed Piloted Hot Air Balloon Experiment:

Altitude Up to 3000 Feet on June 28, 2017

Seismicline

Trilliumx2 AcquisitionMicrophones

x2

Barometer

Needofsyncrhonization

ISAE

JPL


Super

Pressure

Balloon

Flight

• Conduct tropospheric test flight collecting infrasonic data over

remote area

• Develop payload system

• Complete test data analysis

• Compare measured and modeled infrasound signatures

Phase 2 on Earth


Prior Evidence of Ground Detection of Seismo-Acoustic Waves Generated by Earthquakes

Probing the Interior Structure of Venus 34

the bottom ones show pressure variations recorded at the same time; the two signals are

remarkably similar over a wide frequency range—the infrasonic signal is really a seismic signal.

The rapid growth in the number of Infrasound Monitoring Stations (IMS) over the last

decade complemented by expansion of regional networks such as those in Utah, has led to a

rapidly expanding knowledge of the acoustic signatures from not only earthquakes55

but also

volcanoes56

and meteors57

. In the case of earthquakes, this has recently resulted in more detailed

knowledge of the mechanisms by which seismoacoustic waves are generated. Studies of small

earthquakes such as the Circleville Utah, magnitude 4.7 event of January 3, 2011, which was

observed by all nine stations or the University of Utah’s infrasound array,58

have been

particularly useful. Two of the participants in the workshop (Arrowsmith and Blom) have been

actively involved.

This trace of a small earthquake (Figure 6-2) was detected at all nine stations of the array,

which extends across much of the state of Utah. The large signals in the spectral range 1 to 5 Hz

bounded by the red lines are ‘epicentral sound’ signatures that propagate entirely within the

atmosphere. The red lines denote group velocities of 0.34 and 0.22 km/sec). These epicentral

sound signatures were not seen at the three closest sites because there was no ducting of sound to

these locations. The other signatures that are prominent for the closer stations but occur for more

distant stations also correspond to ground-air coupled infrasound resulting from Rayleigh waves

(see Figure 4-10).

These investigations provide great insight on the mechanisms of generating seismic waves

for earthquakes of smaller amplitude. Although a much smaller fraction of the seismic energy is

coupled into the Earth’s atmosphere than would be the case on Venus, it is still sufficient for

detection of comparatively small events. Accordingly, the instrumental and analytical framework

is in place for applying seismoacoustic techniques on Venus.

Figure 6-2. Centerville earthquake 2011. Signals from the nine stations in the University of Utah array are shown. This is filtered data in the 1 to 5 Hz passband.

Epicentral

infrasound

Local

infrasound

Centerville Earthquake 2011 M 4.7 . Signals from the nine stations in

the University of Utah infrasonic array (1 to 5 Hz)

Epicentral infrasound from a M 4.7 earthquake was detected

at six infrasound stations extending up to 500 km from the

source

Sta

tion ID

Time (Min)0 453015

Reproduced from the paper by

Arrowsmith et al 2012)


Proposed Oklahoma Test Site

Map of Oklahoma

The site chosen for this test is the north-eastern corner of the state of

Oklahoma where the frequency of earthquakes is the highest in the nation as

a result of pumping of waste water from oil drilling into geological formations.

Notional Stratollite

footprint


Perspectives for Venus

Use of two barometers

(A) enables spatial filtering for separating

an upward traveling wave associated

with a quake from other sources of

pressure variability.

(B) In addition, infrasound waves

generated by Venus quakes are

faithful replica of seismic waves.

A

B


Looking Ahead: Airglow Mission

Our mission concept VAMOS (Venus Airglow Measurement

and Orbiter for Seismicity) will measure atmospheric

perturbations from an orbiting platform that could provide a

breakthrough in detecting seismicity on Venus and in the

monitoring of seismic wave propagation.


Simulation of Signal from Venus Seismic Event


Conclusions

Balloon Experiments:

• We develop a novel technique and a balloon mission opportunity

for studying the seismicity and interior structure of Venus.

• The new technique will help discriminate for the first time between

quakes-induced signals and background with magnitudes ~3

and above on Venus.

Airglow Mission Concept:

• We expect to launch SmallSat (<180 kg) into high earth orbit as

rideshare with larger spacecraft

• Our mission concept VAMOS (Venus Airglow Measurement and

Orbiter for Seismicity) will measure atmospheric perturbations

from an orbiting platform that could provide a breakthrough in

detecting seismicity on Venus and in the monitoring of seismic

wave propagation.


Acknowledgements

The research is funded by KISS and JPL R&TD program and carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

Copyright 2017. All rights reserved. Government sponsorship acknowledged.


BACKUP SLIDES


Balloon Infrasound Objectives

• JPL in collaboration with ISAE and Caltech Campus is in a process of developing an instrument to measure seismic activity on Venus by detecting infrasonic waves in the atmosphere.

• The overall objective of this research is to demonstrate the feasibility of using sensitive barometers to detect infrasonic signals from seismic and explosive activity on Venus from a balloon platform. Because of Venus’ dense atmosphere, seismic signatures from even small quakes (magnitude ~3) are effectively coupled into the atmosphere. The seismic signals are known to couple about 60 times more efficiently into the atmosphere on Venus than on Earth.

• Our specific objective is to use two or more infrasonic sensors using barometers on a tether deployed from the balloon in a series of Earth-based tests.


VWE Stated Stratollite Capabilities

Courtesy: https://worldview.space/fly-your-payload/

https://worldview.space/fly-your-payload/


Using Seismic Waves to Map Interior Structure of Venus

KISS VENUS-11

Nightside Airglow

imaging

Balloon(s) @ 55 km


Wave-Propagation Global Ionosphere-Thermosphere Model (WP-GITM) Derived TEC Perturbations

Meng et al., 2015

Meng et al., 2017 (in

preparation)

[not to scale]For Tsunamis For Earthquakes

Input II

Tsunami wave

characteristics

Input I

solar wind

conditions, solar

irradiance, auroral

particle

precipitation

Input II

vertical velocity

data

Output

Ionospheric and

thermospheric

disturbances

Documents

Advances in Planetary Seismology Using Infrasound and ... · Aug 15 to 17, 2017 LCPM-12 Conference, Pasadena, CA 1 Advances in Planetary Seismology Using Infrasound and Airglow Signatures